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What is the Most Rain to Ever Fall in One Minute or One Hour?

By: Christopher C. Burt, 5:15 AM GMT on June 02, 2013

What is the Most Rain to Ever Fall in One Minute or One Hour?

As a follow up to my last blog I thought I would write up a short summary of the most intense short-term rainfalls on record in the United States. Wiley Post Airport in Oklahoma City picked up 3.10" in 1 hour and 2.00" in 35 minutes during the tornado and flood event on May 31st.

This spring has seen some phenomenal heavy rain events (as outlined in my previous blog). Some of these included very intense short-term precipitation totals such as the 2.00” in 35 minutes in Oklahoma City on May 31st and 0.69” in 3 minutes (5:26 p.m.-5:29 p.m.) at Houston’s Hobby Airport on April 27th and 0.71" in 13 minutes at Paducah, Kentucky the morning of Saturday, June 1st (4:53 am.-5:06 am.). NOTE: The 5.64" 24-hour rainfall on May 31st in Oklahoma City brought the May total to 14.52", a monthly record and just short of the all-time wettest month (any month) on record of 14.66" set in June 1989.

How do these stack up compared to the all-time U.S. records for short-term rainfalls?

Below is a table of the most intense rainfalls on record over various periods of time:



Table reproduced from my book 'Extreme Weather: A Guide and Record Book'.

One-minute rainfalls

It is hard to imagine how an accurate measurement of precipitation over a 60-second period can be made. However, the U.S. Weather Bureau conducted several exhaustive studies of the Unionville, Maryland claim to 1.23” in one minute on July 4, 1956 and determined it to be accurate (see for the Monthly Weather Review summary). A recording rain gauge: A Friez Universal Type with a 12-inch capacity, dual traverse pen, and 24-hour clock gear on a chart drum was used to make the measurement. It had good exposure and measured a storm total of 3.60” between 2:50 p.m and 11:30 p.m. with 2.84” of this falling in a 50-minute period between 2:50-3:40 p.m. The minute that ostensibly measured the 1.23” total occurred around 3:22-3:23 p.m. Here is a copy of the trace:



Although invisible in this reproduction, there is apparently a faint line on the original trace which is when the excessive rainfall occurred. From ‘Monthly Weather Review’, August 1959 p. 304.

A number of experiments were made on the gauge to determine its calibration and accuracy. The gauge passed all the tests to which it was subjected. Anecdotal information also played a part in the record’s certification. Extreme flash flooding and erosion were reported in the surrounding area and the sky became so dark that residents were forced to turn lights on in spite of being mid-afternoon. Roof gutters were overwhelmed, with water reported flowing off roofs “like Niagara Falls”.

The Unionville figure is generally considered not only the U.S. record for one minute but also the world record for such. A much-quoted 1.50” at Barot, Guadeloupe on November 26, 1970 cannot be verified (in fact, there appears to be no such location on the Caribbean island).

Other significant one-minute rainfalls include 0.69” at Jefferson, Iowa on July 10, 1955 and 0.65” at Opid’s Camp, California on April 5, 1926. At Jefferson 1.00” fell in 109 seconds.

Other amazing short duration rainfalls

The officially recognized U.S. rainfall for a 5 minute period was the 2.03” reported at Alamogordo Creek, New Mexico on June 5, 1960 (3.09” fell in 15 minutes). Fort McPherson, Nebraska reported 1.50” in 5 minutes on May 27, 1868 as did Pensacola, Florida on May 2, 1937. Patterson, New Jersey measured 1.64” in 8 minutes on July 13, 1880. Tyler, Texas reported 2.00” in 10 minutes on April 29, 1905. At Cambridge, Ohio a reputed 7.00" of rain fell in just 30 minutes on July 16, 1914. William G. Hoyt relates in his classic book Floods (Princeton Univ. Press, 1955) that "some persons caught in the open during the storm were actually alarmed for fear they would suffocate, the rain was falling so fast that they had to shield their noses so they could breathe". (p.25). Guinea, Virginia in Caroline County 8 miles southeast of Fredericksburg, reported 9.25" of rain in 40 minutes on August 24, 1906. The validity of the above measurements is open to question.

What is the greatest one-hour rainfall in the U.S. or World?

This is a matter of debate. There appear to be no ‘official’ records for such since each of the proposed cases has its own flaws. The most commonly cited figure is 12.00” at Kilauea Plantation, Kauai, Hawaii on January 24, 1956. This was part of a state record 24-hour rainfall that totaled at Least 38.00” on January 24-25 that year. However, the observer noted that the gauge was overflowing at several times during his observation cycle so the actual figures may have been considerably higher. The storm total was 43.5" apparently all within a 24-hour period but confusion reigns as to the details concerning this event.

Another contender is the 12" in 42 minutes at Holt, Missouri on June 22, 1947. This report has the details.. This is also accepted as a world record for the time span of one hour. Not too far away from Holt, Plainville, Illinois picked up 8.40" in 40 minutes between 6:05 and 6:45 p.m. on May 22, 1941.

A severe thunderstorm at Catskill, New York was reported to have dropped at least 10” of rain in one hour on July 16, 1819 according to bucket surveys.

The most intriguing candidate, however, is for a location (not identified with a specific town) in central West Virginia on the night of August 4-5, 1943. A U.S. Army Corps of Engineers storm report claims that 13.80” of rain fell in one hour between 11:30 p.m and 12:30 a.m. the night of August 4-5. This was measured by a remote gauge simply named No. 86. It appears to have been located near the town of MacFarlon (which measured 5” in 1 hour) in Ritchie County. Another gauge identified as No. 48 picked up 14.6” of rain in about one and a half hours. Curiously, a U.S. record of 19.00" in 2 hours and 30 minutes was measured at Rockport, West Virginia (Wood County) on July 18, 1889 which is only 15 miles west of MacFarlon. This begs the question of just why this part of the state seems prone to extreme precipitation events.

Woodward Ranch, Texas (about 17 miles northwest of D'Hanis, which is 40 miles west of San Antonio) measured an amazing 10.00" in 1 hour, 15.00" in 2 hours and a world record 22.00" in 2 hours and 45 minutes on May 31, 1935 between 3:00-6:00 a.m. This was an especially interesting event since, just hours earlier, a rain gauge in eastern Colorado (at a location 25 miles northeast of Colorado Springs) measured 24" of rain in a 6-hour period between noon-6:00 p.m. May 30th (22.80" of which fell in just 4 hours). Several other gauges in eastern Colorado also measured amounts close to this, lending creditability to the figure. The ensuing floods drowned 21 in this sparsely populated part of the state and the $100 million (adjusted for inflation) flood damage remains one of the costliest natural disasters in Colorado history. Naturally, extreme flooding ensued. The Weather Bureau’s Climatological Data, Colorado Section, May, 1935, reported the following in the Monthly Review:

"On the 30th, excessive local downpours occurred in the vicinity of Colorado Springs and along the northern slope of the Arkansas-Platte Divide...At the height of the flood, skies over extreme eastern counties (where the phenomenal rainfalls were recorded) were a chocolate brown. This was due to a most unusual situation. Along the Colorado-Kansas border there was a heavy dust storm. Clouds of dust could be seen for miles, while to the west torrents of floodwater roared, and at Bovina, hailstones, some as large as baseballs, were reported to have fallen. The coppery-hued sky cast a brown shadow, giving the scene a weird appearance."



The Monument and Fountain Creeks in Colorado Springs flooded portions of the city sweeping away homes and residents. This was the worst flood in Colorado Spring's history. Photo from Colorado Springs Pikes Peak Library District archives.

Yet another extreme rainfall worthy of mention is that of August 12, 1891 when the mountain town of Campo, California (located just a few miles north of the Mexico-U.S. border at an elevation of 2,800') reported an amazing 11.50" in 1 hour and 20 minutes (and a 16.10" storm total). The average annual precipitation here is just 14.82" and in August a mere 0.51". The observer, a Mr. Gaskill, who was considered reliable, stated that much more rain actually fell but he was unable to empty the gauge fast enough as it overflowed although flood waters undermined the gauge and tilted it a bit. This record has been of great interest to California climatologists since it may represent the most intense rainfall that has ever occurred in the state. The California Department of Water Resources gave it a return period of once in 270,000 years!

World 1-hour precipitation record

A purported 15.78" of rain fell at Shangdi (Sahngdu) Nei Monggol (Inner Mongolia), China on July 3, 1975 in just one hour. This record, along with many from China in the mid 1970's, has been difficult to verify. In a future blog I will look at some of the world point short-duration rainfall records, including those of China which has claim to some of the most amazing statistics in this regard.



The isohyetal map for the storm of August 4-5, 1943 in West Virginia that may have dropped 13.8 in one hour. Page from ‘Storm Studies’, Dept. of the Army, Corps of Engineers.

Another fascinating rainstorm, and perhaps of the greatest intensity on record for anywhere in the world, is the famous Smethport, Pennsylvania event of July 18, 1942. During this event an amazing 34.30” of rain reportedly fell (according to several bucket surveys) in a 12-hour period between midnight August 17th and noon August 18th. Of this, 28.50” fell in 3 hours (9.a.m-noon) and 30.70” in 6 hours. Mountainsides were reported to have their vegetation stripped to bedrock and 11 people drowned in the valley around the town. Other precipitation measurements made in the area included 20.4” in 12 hours at Emporium, PA and 18.5” at Mt. Jewett. An official USWB gauge in Salamanca, New York received 6.7” in 3 hours.



The isohyetal map for the storm of July 17-18, 1942 in Pennsylvania and New York that may have dropped 28.5” in three hours, a world record. Page from ‘Storm Studies’, Dept. of the Army, Corps of Engineers.

You may find it curios that so many of these records seemed to have happened in the 1940s and 1950s. This is not a coincidence. During the 1940s and 1950s the U.S. Government (via the Army Corps of Engineers) was very interested in determining what the maximum possible rainfall rates for any given location might be in order to engineer the massive infrastructure improvements that were being made across the country those decades.



The map above is an approximation of what the absolute maximum amount of rainfall that could possibly fall in a 24-hour period across the U.S. east of the Rockies might be, according to research by the Army Corps of Engineers. The actual measured maximum amounts by state are indicated by the blue dots. These are not official figures but 24-hour precipitation amounts that the USACE observed while investigating their ‘Storm Rainfall’ reports which resulted in a massive 1000-page plus compendium of intense short-duration rainfall observations. Map reproduced from ‘Extreme Weather: A Guide and Record Book’, based upon Army Corps of Engineers data.

Summary

Below is a table summarizing all of the precipitation records mentioned in this blog. Keep in mind that this is a mix of 'official' and unofficial measurements made by various U.S. government agencies.



P.S. This blog has almost exclusively focused on U.S. records. In the weeks to come I will take a look at extreme point rainfall records from around the world and also on those that hold the 24-hour record (a much wider net).

Christopher C. Burt
Weather Historian

Extreme Weather Precipitation Records

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

Reader Comments

Thank you for the finding and posting of such vast info.
1.23"/min.
That would be like standing under a fire hose.
A person could drown in rain like that!

Very interesting post.
Quoting RobDaHood:
1.23"/min.
That would be like standing under a fire hose.
A person could drown in rain like that!

Very interesting post.


Ha! That's interesting?

Consider this.

What if all the water fell in one rain drop?

http://what-if.xkcd.com/12/
Intresting Blog! Exactly how many gallons a minute would that be?
I'm curious why Mt Wai‘ale‘ale on Kauai doesn't show up topping the annual records, since most sources report an average of 452" per year, with (reportedly) 683" in 1982.
Quoting N5IEX:
I'm curious why Mt Wai%u2018ale%u2018ale on Kauai doesn't show up topping the annual records, since most sources report an average of 452" per year, with (reportedly) 683" in 1982.


Mt. Waialeale, although one of the wettest places in the world, has never broken a significant rainfall record of any kind. The U.S. national annual precipitation record was set in 1982 at Kukui (actually on Maui Island, not Kauai as the table states--my error!). In recent decades the avg. annual precipitation at Mt. Waialeale has fallen quite dramatically (the last 30-year POR of 1981-2010 seems to indicated just around 384" per year) and recent research shows that there may be a wetter location in Hawaii: Big Bog on Maui with a 30-year POR average of 404". See my blog on this subject I posted on May 22, 2012.
Can I ask if it would be possible to provide a blog about the 500 year flooding currently occurring in Central Europe?
stalled out trough of low pressure dumped incredible amounts of rain on sw cuba back in the early twentieth century research should be done in the libraries

Quoting CloudyDay11:
Intresting Blog! Exactly how many gallons a minute would that be?


You need per unit area in the calculation.
1"/minute would be 25.4 liters/square meter/minute.

There is a heavier 10-minute rainfall in official records than the 12-minute maximum listed above. According to Local Climatological Data for June 1988 in San Antonio, Texas (you can download this issue from NCDC), there was a very heavy rainfall on 2 June 1988 with the following maximum amounts:

5 minutes 1.56 inches ending at 2240 local standard time
10 minutes 2.56 inches ending at 2242
15 minutes 2.90 inches ending at 2247
120 minutes 3.24 inches ending at 2359 (equal to storm total)

I was about 6 miles east of the San Antonio Airport observation site at that time and the rain was not quite as concentrated in time but was still quite heavy. Fortunately the rain was light except for that 15-minute period so it was not a damaging flood. I didn't realize that the 10-minute total was possibly a national record (although the rain rates in several of the longer-time records imply more than 2.56 inches in 10 minutes).

I seem to remember an even heavier officially-recorded 5-minute rainfall, possibly at Charleston, South Carolina, so I will need to do some more searching to locate that.

Also I would be suspicious of most heavy short-term extreme rainfalls at cooperative stations at any time or at official stations before the 1890s or so, since those sites did not have recording rain gauges, even if the total rainfall is correct (or even undercounted if the gauge overflowed).
Quoting RobDaHood:
1.23"/min.
That would be like standing under a fire hose.
A person could drown in rain like that!

Very interesting post.


Pretty much... nice way to put it.

Thanks for the great info WH..
I'm surprised that New Orleans isn't on there.
Referring to comment 10, I tracked down the heavy rain information for Charleston, SC. This was at the Custom House (city location), not at the airport, but was and still is an official US Weather Bureau / National Weather Service site. Even in 1970, this site did not take full observations and mostly used recording instruments.
The short-term precipitation amounts are published in Climatological Data National Summary, 1970 annual summary issue, page 17. The date is 24 August but the ending times are not stated:
Minutes Maximum precip. (inches)
5 2.72
10 2.73
15 2.75
20 2.77
30 2.79
45 2.99
60 3.31
80 3.70
100 4.04
120 4.19
150 4.32
180 4.38
From Local Climatological Data for August 1970 for this site (labeled as CHLS or 13782; the site called CHS or 13880 is the airport), hourly precipitation amounts are given as 3.01, 0.74, and 0.60 inches ending at 1800, 1900, and 2000 (or 6, 7, and 8 PM), with lower hourly amounts for several hours before and after this time, and additional shower periods on the 25th, with 5.05 inches on the 24th and a maximum 24-hour amount of 6.03 inches on the 24th and 25th.
Note that the 5-minute and 10-minute amounts exceed the values in Burt's table, and almost all of the rain in the heaviest 30-minute and shorter periods occurred in 5 minutes.

I also found an exceptional rain at Huron, SD on 18 June 1967. This does not exceed any of the values in the table, but is unusually heavy for South Dakota:
Minutes Maximum precip. (inches)
5 1.05
10 1.75
15 2.45
20 2.80
30 3.42
45 3.73
60 3.83
80 4.83
100 4.93
120 4.98
150 5.08 (same for 180 minutes)
The maximum 24-hour rain was 5.48 inches.

According to station histories in annual summary issues of Local Climatological Data, Huron had a tipping-bucket and a weighing rain gauge, in addition to a nonrecording gauge, but Charleston Custom House had only a tipping-bucket rain gauge.
A tipping-bucket gauge has 2 compartments on a pivot below the funnel that collects the rain. After each 0.01 inch of rain, the bucket tips and empties into a container, exposing the other compartment, and the tipping produces an electrical signal to make a mark on a moving paper strip. With very heavy rain, the bucket does not tip fast enough, and in extreme cases the marks on the paper cannot be distinguished, but the collected rainfall after the storm would be used to determine the total rainfall, and the undercounted rain would be added to the recorded rain rate during the heavier rain periods. If a station has multiple rain gauges, the total precipitation from each gauge could be further used to determine if any gauge has a significant error.
I've been trying to think of a process that would concentrate atmospheric moisture enough to condense out 1" of rain in a minute and I can't! I can imagine a foot of rain in an hour but not an inch in a minute!
Quoting CloudyDay11:
Intresting Blog! Exactly how many gallons a minute would that be?


This amount of rain falling on a house of 1500 sq ft house roof would be 1150 gallons. That's 20 gallons every second. Imagine 4 guys with a 5 gallon pail standing on your roof, each emptying one pail a second on the roof. Or someone dumping a 55 gallon drum of water on the roof every 3 seconds. Impressive. The gutters might just get torn off the house and leave the scene.
Quoting AggieSteve:
Referring to comment 10, I tracked down the heavy rain information for Charleston, SC. This was at the Custom House (city location), not at the airport, but was and still is an official US Weather Bureau / National Weather Service site. Even in 1970, this site did not take full observations and mostly used recording instruments.
The short-term precipitation amounts are published in Climatological Data National Summary, 1970 annual summary issue, page 17. The date is 24 August but the ending times are not stated:
Minutes Maximum precip. (inches)
5 2.72
10 2.73
15 2.75
20 2.77
30 2.79
45 2.99
60 3.31
80 3.70
100 4.04
120 4.19
150 4.32
180 4.38
From Local Climatological Data for August 1970 for this site (labeled as CHLS or 13782; the site called CHS or 13880 is the airport), hourly precipitation amounts are given as 3.01, 0.74, and 0.60 inches ending at 1800, 1900, and 2000 (or 6, 7, and 8 PM), with lower hourly amounts for several hours before and after this time, and additional shower periods on the 25th, with 5.05 inches on the 24th and a maximum 24-hour amount of 6.03 inches on the 24th and 25th.
Note that the 5-minute and 10-minute amounts exceed the values in Burt's table, and almost all of the rain in the heaviest 30-minute and shorter periods occurred in 5 minutes.

I also found an exceptional rain at Huron, SD on 18 June 1967. This does not exceed any of the values in the table, but is unusually heavy for South Dakota:
Minutes Maximum precip. (inches)
5 1.05
10 1.75
15 2.45
20 2.80
30 3.42
45 3.73
60 3.83
80 4.83
100 4.93
120 4.98
150 5.08 (same for 180 minutes)
The maximum 24-hour rain was 5.48 inches.

According to station histories in annual summary issues of Local Climatological Data, Huron had a tipping-bucket and a weighing rain gauge, in addition to a nonrecording gauge, but Charleston Custom House had only a tipping-bucket rain gauge.
A tipping-bucket gauge has 2 compartments on a pivot below the funnel that collects the rain. After each 0.01 inch of rain, the bucket tips and empties into a container, exposing the other compartment, and the tipping produces an electrical signal to make a mark on a moving paper strip. With very heavy rain, the bucket does not tip fast enough, and in extreme cases the marks on the paper cannot be distinguished, but the collected rainfall after the storm would be used to determine the total rainfall, and the undercounted rain would be added to the recorded rain rate during the heavier rain periods. If a station has multiple rain gauges, the total precipitation from each gauge could be further used to determine if any gauge has a significant error.


Thanks for this AggieSteve. This is really great info!

Quoting BaltimoreBrian:
I've been trying to think of a process that would concentrate atmospheric moisture enough to condense out 1" of rain in a minute and I can't! I can imagine a foot of rain in an hour but not an inch in a minute!

Wet microbursts could do it.    The condensation doesn't happen in a minute. The condensation happens over a period several tens of minutes prior to the rain starting but updraft speed exceeds or cancels raindrop fall speed so the cloud increasingly fills with grown raindrops. When the updraft weakens or a downdraft starts, a whole bunch of rain blasts down at once.   This is common to general in thunderstorms and 1"/minute is on the envelope for intensity only.

Downdraft speeds are ~50mph, several times the fall speed of raindrops
so the intensity increases by a factor of "several" if it's raining in
the downdraft (which is again general)


Quoting georgevandenberghe:


Wet microbursts could do it.    The condensation doesn't happen in a minute. The condensation happens over a period several tens of minutes prior to the rain starting but updraft speed exceeds or cancels raindrop fall speed so the cloud increasingly fills with grown raindrops. When the updraft weakens or a downdraft starts, a whole bunch of rain blasts down at once.   This is common to general in thunderstorms and 1"/minute is on the envelope for intensity only.

Downdraft speeds are ~50mph, several times the fall speed of raindrops
so the intensity increases by a factor of "several" if it's raining in
the downdraft (which is again general)




That can work. I see it. Thanks georgevandenberghe.
weatherhistorian has created a new entry.
Christopher:
I found a map that seems to show a location for "Barot" in Guadaloupe.
It puts it here: 16.250032, -61.446469

Interestingly enough, this map came from MIchelin.
http://www.viamichelin.com/web/Maps/Map-Barot-_-G uadeloupe-Guadeloupe?strLocid=31NTE3eDlhMTBjTVRZdU 1qVXdNVEk9Y0xUWXhMalEwTlRrPQ==

Not sure that this makes the reading any more valid. The WMO and the NWS HDSC still seem to not recognize the observation.
21. oaww
http://www.harriscountyfws.org/ Harris County Flood Control District (Houston Texas)

Houston is a wet place this year. I drove through some VERY heavy rain yesterday (Sept 5, 2016). I checked on the Harris County Flood Control site to see just how hard it was raining. They have rain gauges sprinkled across Harris county, so I was able to find one that showed 0.32 inches in 5 minutes. I would not enjoy driving through heavier rain!

The main point is that detailed rainfall data is available for Houston. The 5 minute data on the web evaporates quickly. I do not know if it is archived. But it is a public resouce that you may find interesting!