Average daytime temperatures in May rise from around 16.5 ºC at the start of the month to about 18.5 ºC during the final ten days of the month. Average night minimum temperatures rise from 6.8 ºC to 9.5 ºC. The mean temperature for the month as a whole is 12.7 ºC. Air temperatures in May occasionally rise as high as 27 ºC at Whiteknights. Here, warm May days have seen temperatures as high as 28.5 ºC on 28 May 2005. Seven days at the warmer London Road site had May temperatures rising above 30 ºC - with 31.9 ºC and 31.3 ºC on 29-30 May 1944 (the intervening night having a minimum temperature of 16.6 ºC). May is the first month of the year to see what many would think of as warm spells (daily maximum temperatures reaching 25 ºC on five or more consecutive days). But in early May the maximum temperature can fail to reach 10 ºC - on 1 May 1979 the maximum was just 7.2 ºC, while in May 1962 the temperature failed to rise above 8.9 ºC as late as the 26th. Air frost can still occur in May - since 1908 there have been 31 mornings with an air frost during the month, with the temperature down to -2.0 ºC on 9 May 1980. Monthly mean temperatures in May have varied between 14.5 ºC (1992) and 9.8 ºC (1996). Air frosts have occurred in 23 May months in Reading, with the greatest number of air frosts (3) in May occurring in the cold May of 1941. Ground frosts can remain a severe problem to growers during May, occurring on average on about 8 nights at Whiteknights.
The monthly mean rainfall for May in Reading is about 44 mm. In 2020 only 1 mm of rain fell during May, while May 1967 was the wettest May in the record with 113 mm. Daily falls of 25 mm or more occur in about one year in eight in May, the wettest May day being 21 May 1932 (37.1 mm of rain fell on this day). In May 1915 there were two wet days with 27.7 mm falling on the 13th and 32.0 mm on the 17th.
The duration of bright sunshine in May is close to 198 hours on average with about 2 days being sunless. In 2020 345 h of sunshine occurred (this is the sunniest of any calendar month in the record) while the dull May in 1991 saw only 119 h. Occasionally (1960 and 1984) there are four-day long sunless spells.
Snow is rare in May, having occurred in six May months in the entire record, namely in 1935, 1945, 1955, 1967, 1979 and 1997. The latest dates on which snow fell were the 17-18 May 1955. Lying snow has not been observed at 0900 GMT in May (although the ground condition after the snowfall in May 1945 is unknown). Thunder is heard on 11 days every ten years (on average) in May. One year in five is thunder-free in May while there were 11 days with thunder in May 1969. Fog is observed at 0900 GMT in about one May in five.
All averages refer to the period 1991-2020 unless otherwise stated.
Statistics last updated 1 August 2022.