|Above: The Death Valley weather station. The temperature instrument is housed in the white box on the right. Image credit: Jeff Masters.|
July 2018 has been one of the hottest months in California history, and in Death Valley, California, the temperatures were so extreme in July that they set a new record for the hottest month ever known to have been reliably measured at any station on Earth: an average temperature of 108.1°F (42.3°C). According to WU weather historian Christopher C. Burt, this beats the previous U.S. for all-time hottest month, set just last year (July 2017), of 107.4° (41.9°C)—also at Death Valley. It also beats the previous world record of 107.8°F (42.1°C) set in July 2017 at Dehloran, Iran, according to weather records expert Maximiliano Herrera.
Update (August 8): The above paragraph has been revised to reflect additional research showing that an apparent 108.5°F (42.5°C) average at Dehloran, Iran, in July 2000—mentioned in the original version of this post as the presumed world record holder—was too high due to missing data. See this detailed post by climatologist Brett Brettschneider for more.
|Figure 1. Diary of a scorching week: temperature, dew point, and relative humidity at Death Valley for the week-long period starting on the morning of Tuesday, July 24, 2016, and ending on the morning of July 31. Temperatures dipped below the 100°F mark for just two hours during this entire period, early on July 27. (The low of 95°F on July 24 occurred just prior to the starting time of this plot). Image credit: NWS.|
According to Mr. Burt, the week of July 24 – 30, 2018 was the second hottest week on record for Death Valley (excluding the bogus period of 1913 – 1924; the observer on staff during this time was later found to have made unreliable observations). Only the week of June 28 - July 4, 2013 was hotter. Here are the temperatures recorded at Death Valley during the week of July 24 – 30, 2018; an asterisk* indicates a daily record beaten or tied. During this week, the average high was 125.6°F, the average low was 99.3°F, and the average temperature was 112.4°F:
DATE MAX MIN
7/24 127°F * 95°F
7/25 127°F * 102°F *
7/26 127°F * 100°F
7/27 127°F * 94°F
7/28 124°F 101°F *
7/29 124°F 100°F
7/30 123°F 103°F*
(Update: The week of 7/25 - 7/31 ended up warmer still, with an average temperature of 112.6°F.)
The four consecutive days of 127°F is in second place for the longest such stretch on record at Death Valley. Excluding the unreliable July 1913 data, only a June - July 2013 event beat that, with five such days in a row. Also, daily records for warmest minimum temperature were set on these dates in 2018:
6/25: 97° F
|Figure 2. The official Furnace Creek, Death Valley maximum recording thermometer for the maximum temperature measured on June 30th, 2013. The 129.2°F (54.0°C) reading was the highest reliably measured temperature on Earth. Photo courtesy of Death Valley National Park and NWS-Las Vegas.|
Death Valley: hottest place on Earth
Death Valley recorded Earth's hottest reliably measured temperature on record on June 30, 2013, when the mercury hit 129.2°F (54.0°C). This record was tied on July 21, 2016 when a temperature of 54.0°C (129.2°F) was also recorded at Mitribah, Kuwait. The only higher temperatures ever officially recorded on the planet were measured in Death Valley: July 10, 12, and 13, 1913, when 134°F, 130°F, and 131°F were recorded. This 105-year-old record heat wave has many doubters, though, including Mr. Burt, who noted in a 2010 blog post that "The record has been scrutinized perhaps more than any other in the United States. I don't have much more to add to the debate aside from my belief it is most likely not a valid reading when one looks at all the evidence. Normally when Death Valley records its hottest temperatures they occur during region-wide heat waves. On July 10, 1913, the next highest temperatures recorded in southern California (aside from Greenland Ranch) were just 119° at Heber and 118° at Mammoth Tank." If Mr. Burt is correct, the 129.2°F in Death Valley in 2013 and in Kuwait in 2016 are the hottest temperatures in recorded history on Earth. (The official second hottest place in the U.S. is Lake Havasu City, AZ, which recorded 128° on June 29, 1994, but Mr. Burt says that record is questionable, as are some obviously bogus readings from sites like Salton, CA in the 1880s of 130°). See Mr. Burt’s July 22, 2016 post, Hottest Reliably Measured Air Temperatures on Earth, for more information.
Bob Henson contributed to this post.