WunderBlog Archive » Weather Extremes

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

An Investigation of Death Valley’s 134°F World Temperature Record

By: Christopher C. Burt, 7:06 PM GMT on October 24, 2016

An Investigation of Death Valley’s 134°F (56.7°C) World Air Temperature Record

In 2012 the WMO (World Meteorological Organization) disallowed what had long been considered the hottest air temperature ever measured on Earth: a 58.0°C (136.4°F) reading measured at El Azizia, Libya on September 13, 1922. As a result of this record being struck from the books, the temperature of 134°F (56.7°C) recorded at Greenland Ranch at Furnace Creek in Death Valley, California on July 10, 1913 became, by default, the new world’s hottest air temperature yet measured. In this guest blog we will investigate the credibility of that measurement. This blog is courtesy of William T. Reid, a geographer and climatologist who has been studying the desert climate of California and, in particular, the Death Valley temperature record for some 30 years. Mr. Reid and I worked together to come to a commensurate conclusion regarding the validity of this significant planetary weather record: It is possible to demonstrate that a temperature of 134°F in Death Valley on July 10, 1913, was essentially not possible from a meteorological perspective, using an officially sanctioned USWB shelter and thermometer and following proper procedures observationally. Thus, the best explanation for the record high report(s) in July 1913 is observer error.

The Setting

Death Valley is the lowest, driest and, during the summer months, hottest location in the United States. At its lowest spot, Badwater Basin, the altitude stands at 282 feet below sea level. Some 15 miles north of Badwater and about 100 feet higher is the Furnace Creek oasis and resort. A weather station was established here under the aegis of The USWB (U.S. Weather Bureau) in June 1911, and named ‘Greenland Ranch’. The ranch was developed by the William Tell Coleman Borax Company in 1883, and was named such for the alfalfa fields planted for the mule teams used to transport borax and for feed for other ranch animals consumed by the miners, ranch hands and visitors. In 1934, the oasis area became more commonly known as ‘Furnace Creek Ranch’ and Death Valley became a National Monument. The U.S. Park Service established a weather station in 1934 at their Cow Creek headquarters, three miles north of Furnace Creek. Both Cow Creek and Greenland Ranch stations closed in 1961 when the Park Service set up a new cooperative weather station, again under the aegis of the USWB, at the Death Valley National Park Visitors Center where it remains to this day. This new station, named ‘Death Valley’, is approximately 1000 feet (300 meters) north of the former Greenland Ranch.

A photo of Death Valley from Dante’s View shows the Badwater Basin just below (white area) and the Furnace Creek Ranch and the national park visitors area to the north where the green-shaded area is visible in the top right portion of this image. Photo is a still from the documentary film ‘Dead Heat’ produced by Weather Underground in 2012.

The focus of this investigation is the unprecedented temperature record of July 7-14, 1913 when the USWB COOP observer at Greenland Ranch, Oscar Denton, measured a string of abnormally hot days. Maximum temperatures for July 7-14, 1913, were: 127°, 128°, 129°, 134°, 129°, 130°, 131°, and 127°F respectively. Minimums were near-to-slightly above average for this 8-day period, ranging from 85°F to 93°F. Each daily maximum temperature from July 7 to July 14, 1913 equaled or exceeded all other maximum temperature values at Greenland Ranch for the entire 50-year period of record (1911-1961), aside from a questionable maximum of 129°F in July 1960.

Above is a copy of the actual original COOP form supplied to the USWB by Oscar Denton. Many ‘cleaned up’ copies of this have appeared in other articles concerning the Greenland Ranch record. In fact, a small controversy surrounds this. See for more about the issue concerning the provenance of the original COOP form.

The Instrumentation and its Exposure in 1913

The location for the instrument shelter (a standard Stevenson screen), first installed by the U.S. Weather Bureau in 1911 at Greenland Ranch, was “carefully selected” according to George H. Willson (see Monthly Weather Review, June 1915). Mr. Willson was, at that time, the district forecaster and section director for the U.S Weather Bureau (USWB), Department of Agriculture, San Francisco station and was responsible for climate data in Death Valley during its early years. The shelter housed standard USWB maximum and minimum thermometers, and was well exposed to wind. Structures and trees at the ranch were of sufficient distance to disallow any very localized build-up of hot air around the station during bright sunshine. It was placed “over an alfalfa sod”, and “the location is such that the shelter is not exposed to the reflected heat from the desert.” Willson “italicized” the above quote for emphasis. Willson continued:

“Evaporation is excessive in this section and liberal irrigation is necessary to maintain plant life; hence, the cooling by evaporation from the surrounding damp ground and live vegetation is probably sufficient to lower the readings of the instruments several degrees. Undoubtedly the temperature down in the desert bottom of the valley is much higher than it is at Greenland Ranch.”

About 100 acres of land here was irrigated for the alfalfa crop and other fruits and vegetables. Willson made it clear that the new station was in a spot that was cooler, perhaps significantly cooler, than the rest of the basin bottom. This conservative siting (with regard to daytime temperature measurement) might not have been welcome by one of the earliest Greenland Ranch COOP observers, Oscar Denton (and may have influenced his observations). In a Historic Resource Study by Linda Greene (1981, see references) it is stated that by the late 19th century temperatures at the ranch “ranged from eight to ten degrees cooler than elsewhere in the valley due to the presence of water, shade trees, and grass in the area.”

Thermometer shelters were routinely placed above grass during the first part of the 20th century, even in extremely arid areas where grass was scarce. It was thought important to have consistent environments around and below the shelters to allow valid and meaningful temperature comparisons from station to station. It goes without saying but needs to be emphasized: a desert weather station above grass is representative of a desert area above grass, and it is not representative of a desert area above a typical, mostly barren, desert surface.

Two photos of the Greenland Ranch USWB weather shelter taken sometime in the early 1920s or perhaps late 1910s. The first image (top) is the oldest known photograph of the weather station (circa late 1910s to as late as 1921) and is looking west. The other photo (bottom) was taken in March 1924 and is looking north. Photos from the NWS Las Vegas archives.

An image of the Greenland Ranch weather station from the 1920s shows the instruments above bare ground. It is not known exactly when the change occurred from “over an alfalfa sod” to “over bare ground” but it seems likely that the shelter was still above the well-irrigated alfalfa field during the summer of 1913. Shelter maximums during July 1913 would have been approximately two-to-three degrees cooler compared to a shelter above bare ground and far from any irrigated areas. The weather stations in and around Furnace Creek have been above bare ground since at least the 1920s. The highest officially observed temperatures since 1913 have been several readings of 129°F (53.9°C). These were observed on July 18, 1960 at the Greenland Ranch location (questionable veracity), and also on July 17, 1998, July 20, 2005, July 7, 2007, and June 30, 2013 at the Death Valley (NP Visitors Center) location. Photographic evidence indicates the actual maximum on this latter date attained 129.2°F. See photo below.

A photograph of the official Death Valley maximum thermometer at time of observation on Monday morning July 1, 2013. The photo shows a maximum of 129.2°F was achieved on June 30th, perhaps the highest temperature ever credibly observed on Earth. A similar reading from Mitribah, Kuwait in July 2016 has yet to be confirmed by the WMO (U.N. World Meteorological Organization). Photo courtesy of Death Valley National Park and NWS-Las Vegas.

Meteorology of Summer Heat Waves in the Death Valley Region

At near 36°N latitude, Death Valley is ideally situated geographically for hot weather during the summer months. At this latitude, subsiding air and clear skies dominate (associated with the northern fringe of the planet’s Hadley cell), and the vast majority of summer days are clear or mostly clear in Death Valley. During the late spring and early summer the jet stream and the associated ‘westerlies’ migrate poleward. With this cooler mid-tropospheric flow shunted well to the north, warm air is allowed to build aloft over the Desert Southwest and the Death Valley region. From June to August monsoon-related moisture and thunderstorms are common in the Desert Southwest, sometimes impacting Death Valley. This weather regime is associated with lower maximum temperatures due to cloudiness, precipitation, and general evaporative effects such as storm outflow. However, Death Valley is far enough north and west to avoid most of the monsoon activity that migrates from the Sonoran Desert. Because of the prevailing subsidence, coupled with the high terrain on all sides of Death Valley, it is difficult for low-level moisture to reach the depression itself. Normally, any low-level moisture mixes out into the drier upper levels of the atmosphere during daytime convection. The high mountain ranges to the west, especially the Sierra Nevada and Panamint Range, effectively cast a cool-season (October-April) ‘rain-shadow’ over Death Valley, so Pacific storm systems usually sweep through with little more than wind and clouds. On average, the basin of Death Valley receives only 2.0”-2.5” inches of rain annually, with less than an inch on average due to monsoon and tropical-related activity from May through September.

Death Valley’s barren surface is typically bone dry in summer, and it warms easily under the high desert sun. Surface temperatures of 200°F have been measured, as was the case on July 15, 1972 when the ground surface temperature reached 201°F; at the same time the shelter air temperature stood at 128°F. Since little solar radiation is utilized for evaporation and transpiration, nearly all ‘incoming’ solar radiation (that is not reflected skyward) heats the ground. Intense daytime heating of the surface creates a relatively hot, near-ground layer of air characterized by very steep lapse rates (a ‘super-adiabatic’ layer). This creates a very unstable environment and a strong vertical exchange of air is required to mitigate and regulate such. By early afternoon any vestiges of overnight cooling have ‘mixed out’ entirely, and there is deep mixing throughout the lower half of the troposphere throughout the region. Above the near-ground ‘super-adiabatic’ layer, the environmental lapse rate is at (or very near) the dry adiabatic lapse rate of 5.4°F per 1000 feet. The unconditionally unstable, deep, mixed layer typically extends up to about the 600-millibar level (about 15,000 feet above the bottom of Death Valley) on nearly every summer afternoon.

A consequence of the deep, mixed layer is a virtual connection between its top and its bottom. Once established and maintained, the entire column warms (or cools) as an entity. Any significant increase in ambient temperature at shelter level (1.5 meters above the ground) would be, and must be, associated with a similar degree of warming of the entire air column. Thus, the temperature typically changes little at desert stations during the hottest hours of the afternoon. Arnold Court, an expert desert climatologist for the U.S. Army in the 1940s (see references), found that shelter temperatures remained within 2 or 3 degrees (F°) of the maximum temperature from about 1:30 p.m. to 5:30 p.m. in Death Valley on July afternoons. The physics of the deep, mixed layer does not allow for the development of area-wide ‘hot spots’ within a region, and it does not allow significant afternoon temperature ‘spikes’ to occur. What it DOES allow is a fairly predictable pattern of temperature in the desert both diurnally and spatially. It promotes a strong correlation, on a regional scale, between daily maximum temperature and elevation.

Llewelyn Williams, a geographer with U.S. Army Natick Laboratories, examined the conditions favoring high surface temperatures at Yuma, Arizona, and determined that the key to high ambient air temperatures is “warm air between 5,000 and 14,000 feet and a well-developed vertical exchange induced during afternoon convection” (1967). The study also found that “there exists an upper limit to what the combination of radiation and ground surface temperature can do in developing high ambient air temperatures”.

This sample sounding from Las Vegas, Nevada (from August 2016) nicely illustrates the typical change in temperature with height in the Desert Southwest on dry summer afternoons. Note that the environmental lapse rate closely approximates the dry adiabatic lapse rate up to the 600-millibar level. Sounding from NWS-Las Vegas.

Williams’ concept of an “upper limit” for maximum temperature applies to all of the Desert Southwest during the summer, including Death Valley. The lapse rate of the deep, mixed layer cannot physically get any steeper above any sunbaked and shallow near-surface layer. Thus the “upper limit” shelter temperature is governed by air temperature thousands of feet above the surface and not by local surface level weather conditions. There are, for all intents and purposes, no small-scale weather features that could cause a significant increase in temperature on a local scale once the atmosphere has mixed out. Of course, there are a myriad of possible local differences in wind, exposure, ventilation, nearby vegetation, terrain, ground cover, and aspect that will cause some small variance in maximum temperatures at any particular place on any particular day. However, these effects are minimized at well-sited weather stations.

The hottest afternoons of summer in Death Valley (and the surrounding region) occur when the air is hottest between about the 850 and 600-millibar levels (5,000-15,000 feet). The upper-level anticyclones (or ‘upper highs’) that are responsible for the hottest weather cover vast areas, and are associated with weak horizontal temperature gradients. Thus, each station in a region is essentially working on the same air mass with regard to maximum temperature potential. The days (and the summers) beneath the strongest upper highs and the warmest temperatures between altitudes of about 5,000 feet and 15,000 feet are the days (and the summers) that are hottest at shelter level. In addition, all stations are affected similarly with regard to departure-from-normal for maximum temperatures because of the broad and homogenous nature of the air mass that is affecting the region.

It is the temperature of the free air thousands of feet above Death Valley that determines just how hot an afternoon at shelter level can become.

When under the influence of such homogenous and well-mixed air masses associated with upper high-pressure domes, all regional weather stations easily attain their ‘upper limit’ temperature on summer afternoons. It is elevation that essentially determines the difference in the maximum temperature between one site and another. These temperature differences are remarkably consistent in the Death Valley region on a day-to-day basis. On occasion, clouds and cooling due to moisture and storms might disrupt the consistency of the regional temperature-elevation relationship (by not permitting some areas to reach their ‘upper-limit’ maximum temperature), but these instances are relatively infrequent in midsummer.

Thus, not surprisingly, for the Death Valley region, there is a strong correlation when plotting station elevations versus:

1) average daily maximum temperatures for summer months

2) average annual maximum temperatures

3) extreme maximum temperatures of record

4) day-to-day maximum temperatures during the hottest summertime periods

Note that summer maximums in the region change with elevation at a rate close to 4.5 degrees F per 1000 feet, a rate not quite as steep as the dry adiabatic lapse rate of 5.4 degrees F per 1000 feet.

The physical characteristics of the atmosphere above the Death Valley region on typical, warm-to-hot and sunny summer afternoons are such that temperature differences from station to station are due almost entirely to elevation differences, and the rate of change with elevation is consistent. Under the influence of a mid-level anticyclone, the departures from average for maximums are generally very similar region-wide. In summer, if the lower-to-mid-troposphere is warm enough to allow only near-normal maximums in the region, then it is not warm enough to cause MUCH-above-normal maximums at ANY location in the region. Heat waves are never localized in summer. Maximum temperatures are quite predictable and are dependent on temperatures between about 5,000 and 15,000 feet. The hottest events are associated with temperatures of about 17°C to 19°C at the 700 mb level. The average and extreme temperature data in the table above are for each station's period of record that varies from site to site. NOTE ABOUT THE TABLE AND GRAPH ABOVE: Problematic and questionable reports, such as the maximums from 128°F to 134°F at Greenland Ranch in 1913 and 1960, were excluded. Also not incorporated in the averages and extremes are data from periods when a station appeared to be inadequately sited (albeit temporarily) and was providing unrepresentative maximums compared to its long-term record. Graphics by William T. Reid.

Comparison of Temperatures at Death Valley to Locations in the Vicinity

There are a number of ways to illustrate how anomalous the Greenland Ranch temperature reports of July 1913 were from a climatological and statistical perspective, for instance:

—-Dr. Arnold Court (“How Hot Is Death Valley?” see references) was skeptical of the record of 134°F as early as 1949, determining that a value that high would be expected statistically only once every 650 years based on the first 37 annual maximums at Greenland Ranch.

—-The diurnal temperature ranges were exceptionally large for July during the first two weeks of July 1913.

—- All annual maximums at Greenland Ranch (1911-1960) were 120°-127°F (aside from 1913 and a suspect 129° in 1960), and all at the Death Valley location (1961-2016) were 119°-129°F. The combined average (of 105 annual maximums) is 124.3°F and the standard deviation of such is 2.2. An annual maximum of 134°F would be a full 4.5 standard deviations from the mean.

The best way to ‘question’ the record maximums of July 7-14, 1913, however, might be to demonstrate that such extremely hot conditions were essentially not possible physically at that time. Based on the surrounding station data, the atmosphere above the Death Valley region was not warm enough to allow authentic maximums near and above 130°F at Greenland Ranch during the second week of July 1913. As mentioned earlier, summertime heat events here are characterized by a strong correlation between elevation and maximum temperature, and are characterized by relatively similar ‘departures from average’ for the maximums at stations in the region. During hot weather, the maximum temperatures at any selected station tend to be very well supported by the maximum temperatures attained at ALL of the surrounding stations. Of course, this is assuming that all of the temperature measurements are valid. This section compares several heat episodes to the one of July 1913.

The nearest (long term) stations to Greenland Ranch with temperature data during its early years of operation were as follows:

To the WEST: Lone Pine and Independence in Owens Valley of California near 3900’ feet in elevation.

To the SOUTH and SOUTHEAST: Barstow, CA and Las Vegas, NV near 2000’.

To the NORTH: Tonopah and Columbia (near Goldfield), Nevada near 6000’.

All the above sites are 75 to 115 miles distant from Greenland Ranch (the weather stations at Independence and Tonopah employed U.S. Weather Bureau observers). The elevation-versus-temperature charts provided in this section include a sloping ‘average lapse rate’ line through each plot for Greenland Ranch. Its slope of 4.5 degrees F per 1000 feet closely approximates the average change of daily maximum temperature with elevation in the region during Julys. Despite the distances involved, if dry and sunny weather prevails AND the data are problem-free, then all stations should plot relatively closely to the average lapse rate line through Greenland Ranch. For that matter, ALL stations should plot relatively closely to a line with the same slope through ANY station plot.

A map illustrating all of the sites mentioned in this blog. Map courtesy of Mark Stroud at Moon Street Cartography.

Summers of 1911 and 1912

Local environments and instrumentation at the regional weather stations were presumably much the same in the summers of 1911 and 1912 as they were for 1913. Comparisons of reliable maximums during the summers of 1911 and 1912 should provide a fairly solid foundation for expected differences between stations in subsequent summers.

In its first two summers of record, (1911 and 1912), Greenland Ranch maximum temperatures were supported by those observed at surrounding stations (Table A and July 1911 plot). The departures from average for the maximums are relatively consistent among the stations during the warmest periods. For the hottest 13-day period in July, 1911 (July 5-17), for example, average maximums ranged from 0.2°F above the July average at Lone Pine to 3.2°F above average at Barstow. Greenland Ranch maximums averaged 1.9°F above average based on its 1911-1930 average of 116.4°F as per the Climatic Summary of the United States, USWB, 1933. The relatively narrow range of departure values among the stations is commonplace, and to be expected during the hotter-than-normal periods in mid-summer. Similarly narrow spreads of departures were the case for the hottest periods during the summer of 1912.

The temperature-elevation plots for the same 13-day period in July 1911 show that four of the five stations plot a few degrees to the left of the average maximum-temperature-versus-elevation line through Greenland Ranch. This might suggest only modest support for the Greenland Ranch maximums, but Columbia plots slightly to the right of the line, offering excellent support. Lone Pine and Independence, in Owens Valley, are both about 6°F off the line on the cool side. Owens Valley was much moister than Death Valley prior to water diversions to Los Angeles that began in 1913. It is not surprising that differences in maximum temperature between the two basins in summer were a bit wider than that which would be expected due only to elevation differences. The different times of observation (5 p.m. at Greenland Ranch and midnight at Independence) would also produce slightly larger differences in average maximums between the two stations.

This plot (for the period of July 5-17, 1911) illustrates fairly consistent support for the Greenland Ranch maximum temperature of 122°F during the July heat wave of 1911 vis-a-vis the other sites reporting temperature data those weeks. Compare this to the 1913 graph several paragraphs below. Graphs produced by William T. Reid.

Daily maximums for June, July, and August for both 1911 and 1912 averaged 23 degrees lower at Independence and 32 degrees lower at Tonopah compared to Greenland Ranch. These differences in average daily maximum temperature are quite reasonable for stations separated by 4185 feet and 6268 feet of elevation, respectively.

The Summer of 1913

An inexplicable change in the correlations and differences mentioned above developed during the spring and early summer of 1913. Greenland Ranch maximums increased to levels not supported by surrounding data (see Table A and charts). For June, July, and August of 1913, maximums at Greenland Ranch averaged 28 and 36 degrees F warmer than at Independence and Tonopah, respectively. This is an increase of four-to-five degrees compared to the differences during the summers of 1911 and 1912. Similar, wider-than-normal differences in average maximums were evident in April and May of 1913 as well.

For the first 15 days of July 1913, the average maximum of 125.7°F at Greenland Ranch was 9.3 degrees F above its average daily maximum temperature for the usual July (Table A and charts). The surrounding stations were generally 2.5 to 4.5 degrees F above average, so the maximums at Greenland Ranch were running about 6 degrees F warmer, over and above the typical differences, than the surrounding sites. The Greenland Ranch maximums depict an unprecedented two-week period of extremely hot weather, while the other stations show a heat wave which might be characterized as ‘better-than-average’ but certainly not ‘extreme’.

The differences are even wider for the hottest 5-day period in July 1913: from the 9th to the 13th. Greenland Ranch maximums averaged 30.4 degrees F higher than Independence and 41.6 degrees F higher than at Tonopah. The table below shows average maximums and departures for July 9th to July 13th:

For the monthly maximums in July 1913, Greenland Ranch's 134°F is 18 degrees F above the July average max temperature, compared to departures of only +7 to +11 degrees F at the nearest stations:

The maximums at surrounding stations would suggest, or support, a daily extreme maximum of about 123°-126°F at Greenland Ranch during the heat wave of July 9-13. Authentic temperatures near and above 130°F in Death Valley are not supported by any of the maximums at the closest stations.

Looking at the station-elevation plots, the surrounding stations fall well to the left of the average temperature-elevation/lapse-rate lines through Greenland Ranch for both the 15-day period of July 1913 and for the extreme daily maximum during the period. If it is presumed that the lower troposphere was very well-mixed in the Death Valley region; and if it is presumed that the maximum temperature data are reliable at the stations surrounding Greenland Ranch; and if it is presumed that the instrumentation at Greenland Ranch was problem-free and in the same place as it was during the summers of 1911 and 1912; then it is difficult to explain the very hot observations at Greenland Ranch during the first half of July 1913, at least from a physical or meteorological perspective.

Compare this to the graph from July of 1911 reproduced several paragraphs above.

Greenland Ranch maximums are a bit more reasonable for the hot period of August 1-8, 1913 (Table A and chart further below in blog), but still seem a bit warmer than what the surrounding stations would support. The hottest periods in 1915 and 1916 show a similar pattern (though not as pronounced as in July 1913), with maximums at Greenland Ranch averaging a few degrees on the high side.

Annual Absolute Temperature Maximums: Summers of 1911, 1912, 1913, 1914, and 1915

At the stations that surrounded Greenland Ranch, the heat wave of July 1913 saw extreme temperature maximums that were near or a few degrees warmer than those of the previous two years (1911 and 1912). In 1913, however, Greenland Ranch jumped up more than ten degrees hotter compared to what was observed there in 1911 and 1912.

Here are the annual maximums (with departure from the July average daily maximum in parentheses) for 1911 through 1915:

NOTE: Oasis Ranch and Lida had too short a period of record to establish mean temperatures. They are included in the above table because they were among the closest sites to Greenland Ranch that were active during this period. (see map).

Although long-term stations near Death Valley saw hotter absolute maximum temperatures in numerous summers compared to 1913, Greenland Ranch never again came close to its record of 134°F observed on July 10, 1913.

Significant Heat Events Post-1913

Here is a summary of some significant heat events in Death Valley in later years, and how the temperatures in Death Valley compared to other sites in the vicinity:

July 16-28, 1931

The last half of July 1931, was especially hot at all of the stations in the Death Valley region. For the 13-day period from July 16 to 28, Greenland Ranch maximums averaged 122.3°F, or about six degrees above its July daily average. Similarly, maximums at the surrounding stations were 6 to 9 degrees above average (Table A and plot). The hottest days at each station were around the 19th and again on the 26th, when Greenland Ranch reported 126°F. In fact, on July 26th Las Vegas reported its highest temperature ever observed: 118°F. A strong correlation during this heat event is evident when the average maximums are plotted against station elevation, and also when the highest temperature for the period is plotted versus elevation.

Again, compare this plot to that of July 1913 earlier in the blog.

July 11-29, 1933

An impressive heat wave gripped the Death Valley region this month. For the 19 days from the 11th to the 29th, Greenland Ranch maximums averaged 123.2°F, nearly seven degrees hotter than its average daily maximum for July. Departures at surrounding stations were similar: +5.9 at Las Vegas, +6.7 at Trona, +7.8 at Independence and Tonopah, and +7.9 degrees at Goldfield. This heat wave was greater in length and intensity than the July 1913 event at Independence, Las Vegas, and Tonopah; yet at Greenland Ranch the maximum of 127°F in July 1933 was well short of its 134°F in 1913.

July 1972 and June/July 2013

The Death Valley weather station (now sited near the National Park Visitors Center) reached impressive maximums of 128°F in mid-July, 1972 and 129°F in late June 2013 (see charts). Maximums at surrounding stations during these heat waves were also near or at record levels, providing support for the reports from Death Valley. Plots of averages and extremes for numerous other notable heat events in the region can be found here. For each event (outside of the period while Denton was the observer) the correlation between temperature maximums and elevation is strong: surrounding stations support the Death Valley maximums and the Death Valley maximums in turn support those at the higher elevation sites.

Data Tables

Below (2nd table down) are listed the average maximum temperatures and the associated ‘departures from the average daily maximum for July’ for the station at Greenland Ranch compared to other sites in the region during the hottest summertime periods from 1911 to 1960.

The departures are based against averages for the stations’ period of record through 1930, if available:


Table A compares departures from average in maximum temperature between Greenland Ranch/Furnace Creek Ranch and surrounding stations for selected significant summertime hot spells in the region.

The first figure for each period is for Greenland Ranch, and is the difference between its average maximum (for the period shown) and its long-term average maximum temperature for July (116.4°F) for the POR of 1911-1930 (*see note below concerning this).

The second figure is the average of the departures of the maximums (compared to July data) at the surrounding stations, namely Independence, Lone Pine, Tonopah, Columbia/Goldfield, Las Vegas, Barstow, Trona and Cow Creek.

The third figure is the difference between the first two values. During typical summertime heat waves, departures in maximum temperature are roughly similar among all of the stations. The difference in departures between Greenland Ranch and the average of the closest stations should usually be close to zero. When the difference is more than a few degrees from zero, as during several of the summers when Oscar Denton was observer at Greenland Ranch, then that suggests problematic or suspect data at Greenland Ranch.

*NOTE: A value of 116.4F is utilized in this table as the average daily maximum temperature for July at Greenland Ranch. This is the figure provided in Summary of the Climatological Data for the United States, by Sections, Weather Bureau Bulletin W, 1912, revised and reprinted in 1933.. This value incorporates the 20 Julys at Greenland Ranch from 1911 to 1930, and is likely artificially inflated by about one degree F because of the suspect maximum temperature reports during the period when Oscar Denton was the observer (for the summers of 1913-1920). The Western Region Climate Center gives a figure of 115.5°F as the average July maximum temperature at Greenland Ranch for the POR (period of record) from 1911 to 1960. Also, note that the data below are relative to averages for July, including the non-July timeframes shown for the summer of 1913 (in order to illustrate the anomalously high temperatures during Oscar Denton’s first summer as the COOP observer).

The actual data for the above figures can be found here.

The USWB COOP Observer at Death Valley in 1913

About September 1912, Oscar Denton replaced Thomas Osborne as the Greenland Ranch USWB COOP weather station observer. Denton, of San Diego, began signing the USWB COOP forms in September, but the first form with data in his handwriting was December 1912. Denton served as the observer, caretaker, and foreman of the ranch for the Pacific Coast Borax Company until mid-August, 1920. Thus, Denton’s first full summer as the weather observer was the summer of 1913. A meticulous examination of the Greenland Ranch climate record during the eight years with Denton as observer reveals an abundance of curious and problematic reports:

—-When rain fell at the ranch, recorded amounts were almost invariably in the amounts of 0.01”, 0.10”, 0.20”, and 0.30”.

—-Minimum temperatures were consistently, and inexplicably much too warm during the winters of 1913-14 and 1914-15. This resulted in unusually small diurnal temperature ranges. The temperature reports during these two winters suggest a striking lack of familiarity with the instruments and/or the standard operating procedures by the weather observer.

—-There were occasional periods when the daily maximum and minimum temperatures would take on a persistent and rather unnatural numerical pattern. These periods would often show poor correspondence in temperature between Greenland Ranch and surrounding stations. As one example, in September 1914, there were 15 consecutive maximums of either 109°F or 110°F (and surrounding stations offer no support to the run of nearly identical maximums). These instances suggest that Denton may have been just ‘filling in the blanks’ for days when he missed taking the observations.

—-When Denton was providing the ‘set max’ temperature at the 5 p.m. observation time, the maximum temperature on the following day was occasionally lower than the ‘set max’ entry provided on the previous day at 5 p.m. This implies that Denton was resetting the maximum thermometer more than once per day, presumably to know the ‘real’ maximum for the day in question rather than for the entire previous 24 hours.

For the period of record when Oscar Denton was observer at Greenland Ranch it is important to emphasize just how problematic the climate record for Greenland Ranch became. Here is a good example: For the period from March 16-20, 1913 a warm spell in the Desert Southwest came to a quick end when a cool and windy weather system swept into California and Nevada. A few stations in the Death Valley region reported small amounts of rain around the 18th, and observer notes mentioned very windy conditions on the 17th and 18th at Columbia, Barstow and Las Vegas. Maximum temperatures fell region-wide by about ten degrees from the 17th to the 18th, yet the maximum at Greenland Ranch on both days was constant at 90°F. Although there was generally little change in maximum temperature from the 18th to the 19th at the closest surrounding stations, the maximum at Greenland Ranch jumped up to 95°F on the 19th. Independence had a high of only 56°F on the 19th, and Barstow reached only 62°F. The increase in the maximum temperatures at Greenland Ranch during this cooling trend strongly suggests that Denton was, perhaps, absent from the ranch and that he estimated the temperatures for the time he was gone. There were no missing days on the COOP forms during Denton’s tenure. Perhaps Denton decided that estimated temperatures were better than blank spaces on the COOP forms. See this link for more on data inconsistencies and problems at Greenland Ranch during the Denton years of observation.

A photograph of Oscar Denton appeared in the magazine ‘Popular Science Monthly’ for their September 1922 edition. It is perhaps the only known photograph of Mr. Denton. Another image (below) in the same article shows an unidentified man, possibly Denton, at the weather shelter. Photos from Popular Science Monthly September 1922 issue (see references).

Was Denton adequately capable and competent to provide reliable data? His supervisor, Fred Corkhill, said that Denton had difficulty reading the tables to determine the humidity from the wet and dry bulb readings in order to properly set the hygrograph. It would appear that Mr. Denton was not scientifically inclined. Was Denton adequately conscientious and motivated to provide reliable climate data? The Greenland Ranch record from 1912 to 1920 would suggest not much. However, it may be that Denton was overly preoccupied with his weather observing duties, and somewhat obsessed with temperature readings at the ranch (especially during the torrid summer months when the ranch and borax works pretty much shut down and Denton was often the only person there). His penchant for resetting the maximum thermometer more than once per day, for entering figures for periods when he was absent, for entering temperatures which appear blatantly false (and on a somewhat regular basis), show that Denton's mindset may have been affecting the observations he entered into the COOP forms.

There is little doubt that Denton enjoyed sharing the stories of intense heat and personal survival in Death Valley with visitors and other employees who rarely visited or worked at the ranch during the summer months. Writer Frank Crampton (see references) had this to say about Denton:

“It was not often that more than one or two of the old timers, prospectors, or desert rats were at the Furnace Creek Ranch at the same time, but Oscar was a good listener, and he passed the latest stories and the best lies to the next to come for the regular cleanup and supplies.”

Denton was likely proud that he was one of the few who could tolerate the heat of Death Valley and survive an entire summer (let alone many) there as caretaker. If, as the old-timers related, the temperature at the ranch would sometimes soar into the 130°s and 140°s, then his stories of surviving the hottest summer days when the temperature hit ‘only’ 125°F at the official weather station might have fallen a little flat.


1) Greenland Ranch temperatures not consistent with meteorological conditions in July 1913

The temperatures reported at Greenland Ranch during the period of hot weather from July 7-14, 1913 were not consistent with meteorological conditions in the region at the time of observation. There is no indication that an exceptional heat wave was occurring in the Southwest U.S. during this period. ‘Isolated hot spots’, whether a result of wind patterns or local geography, cannot account for the exceptional temperatures reported at Greenland Ranch given known meteorology of Death Valley during extreme heat events.

As a footnote to this, it is interesting to quote Mr. George H. Willson (who first reported the record in the Monthly Weather Review for June 1915): “The daily weather maps have been carefully studied for some peculiarity that would explain the extremely hot weather in Death Valley in July 1913, but it is doubtful if a sufficient cause was found. The weather type was that which always causes high temperatures over the south Pacific coast district, it was not unusually pronounced, and did not give record temperatures in any other portion of California.” He went on to say, “The condition was probably local as is often the case in mountainous regions, and the exceptionally high temperatures were confined to Death Valley”. We now know that this could not have been the case, since no heat event in Death Valley has ever, in over 100 years of observation, confirmed such a possibility.

2) Lack of correspondence with surrounding weather sites at time of July 1913 observations

The extreme temperature of 134°F measured on July 10, 1913 did not correlate with observations at other sites in the region on this date and likewise for the entire period of the extreme temperature readings reported from Greenland Ranch during the week of July 7-14, 1913. During several other periods during the time that Oscar Denton was the observer at Greenland Ranch temperatures were often, although not always, at odds with the surrounding site observations. Given the maximums at the surrounding stations in July 1913, the atmosphere was never hot enough to support authentic air temperatures as high as 134°F at Furnace Creek in Death Valley.

3) Concerns with observer’s credibility and experience

Since the record hot observations at Greenland Ranch from July 7-14, 1913 cannot be explained meteorologically, it is the conclusion of this investigation that the observer, Oscar Denton, knowingly or inadvertently exaggerated the maximum temperatures during that time frame. This likely was the result of his lack of experience as an official USWB observer coupled with a strong notion that the temperature readings from the USWB instrument shelter, above the cooling influence of the irrigated alfalfa sod, were inadequate. Given the much higher temperatures indicated on other household thermometers at the ranch, Mr. Denton may have been of the opinion that the ‘official’ Stevenson screen observations were not accurately representing the extreme heat which he felt was self-evident. The heat wave in July 1913 was the first such he was ‘in charge of’ as an official COOP observer and perhaps he was not familiar with temperature measurement in a controlled environment i.e. an official USWB-supplied Stevenson Screen and the official equipment (thermometers) that accompany such. Thus he fell back on what he perceived to be his own experience of Death Valley heat and associated temperatures and he consequently exaggerated the temperatures indicated on the maximum thermometer to values he thought were more realistic.

The Greenland Ranch weather station was sited in a very conservative place, a relatively cool place in Death Valley. If the observations of 129°F to 134°F at Greenland Ranch from July 9 to 13 were authentic, then maximums at the closest surrounding stations during that 5-day period would have been substantially hotter than actually observed.

Finally, it is not possible to conclusively prove that Mr. Denton intentionally or inadvertently exaggerated his observations. However, it is possible to demonstrate that a temperature of 134°F in Death Valley on July 10, 1913 was essentially not possible from a meteorological perspective using an officially sanctioned USWB shelter and thermometer and following proper procedures observationally. Thus, the best explanation for the record high report(s) in July 1913 is observer error.


Court, Arnold, 1949: How Hot is Death Valley? Geographical Review, vol. 39, pp. 214–220.

——, 1952: Duration of Very Hot Temperatures Bulletin of the American Meteorological Society, vol. 33, pp. 140–149.

——, 1953: Temperature Extremes in the United States Geographical Review, vol. 43, pp. 39–49.

Crampton, F. A., 1956: Deep Enough: A Working Stiff in the Western Mine Camps University of Oklahoma Press.

Eklund, Ernest E., 1933: Some Additional Facts about the Climate of Death Valley, California. Monthly Weather Review. Vol. 61, pp. 33–35.

Greene, L. W., 1981: Death Valley National Monument, Historic Resource Study, A History of Mining, Volume I Parts 1 and 2 Historic Preservation Branch, Pacific Northwest/Western Team, Denver Service Center, National Park Service, U.S. Department of the Interior, Denver, Colorado.

Harrington, Mark W., 1892: Notes on the Climate and Meteorology of Death Valley, California Weather Bureau Bulletin No. 1, U.S. Weather Bureau.

Hogg, J. E., September, 1922: Welcome to the Hottest Spot on Earth!"Popular Science Monthly, Vol. 101, No. 3, pp. 19-22.

Ludlum, David, 1963: Death Valley Weatherwise, June 1963, pp. 116-117.

McAdie, A. G., 1913: Relative Humidity in Death Valley Monthly Weather Review, vol. 41, p. 931.

Palmer, Andrew, January 1922: Death Valley -- The Hottest Known Region Monthly Weather Review, Volume 50, pp. 10-13.

Potter, Sean, Jul/Aug 2010: Retrospect: July 10, 1913: Highest Temperature Ever Recorded in North America Weatherwise Magazine, Vol. 63, No. 4, p. 14.

Reid, William T., 1987: A Critical Analysis of Eastern Mojave Desert Temperatures. Masters Thesis, California State University Northridge, Geography Department (376 pages).

Roof, Steven and Callagan, Charlie, 2003: The Climate of Death Valley Bulletin of the American Meteorological Society, Vol. 84, No.12, pp. 1725-1739.

Stachelski, Chris, 2013: World's Hottest -- 100th Anniversary of the World's Hottest Recorded Air Temperature. pages 6-7 of PDF document on this Death Valley National Park web site link.

Stachelski, Chris, and Las Vegas NWS Staff, last updated 2016: Climate of Death Valley, California online PDF document from NWS Las Vegas.

Willson, George H., 1915: The Hottest Region in the United States Monthly Weather Review, vol. 43, pp. 278–280, 341.

Williams, Llewelyn, 1967: Climatological Conditions Favoring Occurrence of High Temperatures at Yuma Proving Ground, Arizona Technical Report 67-42-ES, U.S. Army Natick Laboratories, Earth Science Division, Geography Branch, Natick, Massachusetts.

About William T. Reid

William T. Reid studied Geography and Climatology at California State University Northridge. Reid received a B.A. and M.A. in Geography/Climatology from CSUN in 1981 and 1987, respectively. His Masters Thesis, "A Critical Analysis of Eastern Mojave Desert Temperatures," was under the advisement of Dr. Arnold Court and included a detailed scrutiny of the record 134°F report at Greenland Ranch in 1913. Reid has worked as a climatologist and forecaster for a private weather company in Southern California, and has worked as a certified weather observer at several airports in the Los Angeles area since 2004. He currently operates and oversees automatic cooperative weather stations in Chatsworth and at his home in Westlake Village for NWS Oxnard. Reid has studied temperature records in the California deserts and Death Valley region for more than 30 years, culminating with a detailed write-up on his web site that focuses on Greenland Ranch's early temperature record (a work in progress).

KUDOS: Big thanks to Mark Stroud of Moon Street Cartography for production of maps and tables.

Christopher C. Burt
Weather Underground

Extreme Weather Heat Temperature

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.