Places in the World that have Reported 40”+ (1016 mm) of Rainfall within 24-hours<

Places in the World that have Reported 40”+ (1016 mm) of Rainfall within 24-hours

The recent amazing rainfall total of 32.44” (824 mm) from Izu Oshima Island on October 15th, has prompted me to look at what places in the world have measured 24-hour rainfalls of 40” (1016 mm) or more. There seems to some debate as to whether Japan has ever measured such and the list of such places is a short one.

It has been reported that the 824 mm rainfall on Izu Oshima that fell on the calendar day of October 15th was the 3rd greatest 24-hour rainfall on record for Japan (at least measured at an official JMA site). The two heavier falls being 851.1 mm (33.51”) at Yanase, Kochi Prefecture on July 19, 2011 and 844 mm (33.23”) at Takeshi, Nara Prefecture on August 1, 1982. However, I believe Izu Oshima may have actually received as much as 850 mm (33.46”) in a 24-hour period of October 14-15. There have been heavier 24-hour (and calendar day) rainfalls in Japan according to scientific literature (ref: ‘The Climate of Japan’ edited by Elichiro Fukui, Elsevier publications, 1977). In this book the following are listed as Japan’s greatest 24-hour precipitation events:

1109.2 mm (43.67”) Saigo, Nagasaki Prefecture July 25-26, 1957

1011 mm (39.80”) Mt. Odaigahara, Nara Prefecture Sept. 14, 1923

997.4 mm (39.27”) Hase, Nagasaki Prefecture July 25-26, 1957

976.2 mm (38.43”) Zenki, Nara Prefecture Sept. 13, 1954

963.9 mm (37.95”) Mt. Odaigahara, Nara Prefecture July 29, 1946

The storm of July 25-26, 1957 was a result of a tropical storm colliding with what is known as a ‘Bai-u’ : a cold front draped over Japan with deep moist tropical air overrunning it and resulting in tremendous precipitation amounts. This is similar as to what occurred last Tuesday in Japan. Flooding from the 1957 event resulted in the deaths of almost 1000 people.

There is also a report of an even greater rainfall of 1138 mm (44.80”) in 24 hours at a site called ‘Hiso’ in Tokushima Prefecture on September 11-12, 1976 but I can not find any scientific references to this event nor any information about the site itself. Maximiliano Herrera has looked at official JMA data for nearby sites and it seems to be a dubious figure (as do the other sites listed in Dr. Fukui’s book).

Below is a list of all the places in the world that have reportedly received at least 40” (1016 mm) of precipitation in a single 24-hour period. It should be noted that some of these are of questionable veracity (especially those I’ve marked with an asterisk ‘*’). Also, the exact amounts vary from source to source. For most weather sites, accurately measuring such prodigious rainfalls over such a short time span is problematical. Places that ‘regularly’ see such rainfall, like on Reunion Island in the Indian Ocean, have special recording gauges to accommodate such rainfalls but most sites do not.



A photograph of Cilaos on Reunion Island off the coast of Africa in the Indian Ocean. This site may be where the heaviest 24-hour rainfall ever measured on earth occurred (73.62”/1870 mm) during a tropical storm on March 15-16, 1952. The figure, however, is not acknowledged by Meteo France which maintains climate data for the island. Photo from Wikicommons.

For example, the 43” reported from Alvin, Texas during Tropical Storm Claudette on July 25-26, 1979 was measured by a resident, Paul Davison, at his home using a household rain gauge. He actually reported a 45” storm total of which 43” fell between noon July 25th and noon July 26th. The NWS office sent a team to the Alvin area where they made a ‘bucket’ survey (measuring how much water had filled various containers, like empty oil drums, garbage cans, etc.) to compare to Mr. Davison’s measurements. Apparently the team came away convinced they were accurate and official enough to constitute a new national record for the U.S.



Results of the bucket survey made by the NWS team in July 1979 from the greater Houston, Texas area. A location in the suburb of Alvin reported 43” (1092 mm) over one 24-hour period during the storm. Map from ‘Weatherwise’ magazine August 1980 issue.

In any case, here for better or worse, is the most complete list of locations having reported 40” + 24-hour rainfalls that I can put together so far:



NOTE: The Cherrapunji figure of 49.07” on June 15-16, 1995 is derived from a two-day total of 2493 mm (98.15”) on June 15-16, 1995. The WMO is currently investigating this figure as a possible world record for a two-day measurement. What the maximum in 24 hours might have been has not yet been disclosed.


REFERENCES Most of the Chinese and Taiwan figures come from ‘Monsoons over China’ by Ding Yihui, Kluwer Academic Publishers, 1994. The Reunion rainfalls come from BAMS Dec. 1997, BAMS May 2009 and Monthly Weather Review Jan. 1950 ‘World’s Greatest Observed Point Rainfalls’ and MWR Feb. 1965 ‘Indian and Taiwan Rainfalls set New Records’ both articles by J.L.H. Paulhus. For the Alvin, Texas data see ‘Weatherwise’ magazine Aug. 1980 ‘An Apparent new Record for Extreme Rainfall’ by Jerry D. Hill. Japanese rainfall statistics from 'The Climate of Japan' by E. Fukui, Elsevier Publications, 1977.

Christopher C. Burt
Weather Historian