May 2012

Temperatures
(all temperatures in degrees Celsius; all averages 1961 – 1990)

Mean daily maximum: 15.0
Difference from average: +0.7

Mean daily minimum: 5.4
Difference from average: -0.2

Mean air temperature: 10.2
Difference from average: +0.3

Absolute maximum: 25.2 (28th)

Absolute minimum: -2.0 (6th)

Mean grass minimum: 3.3

Absolute grass minimum: -5.1 (5th)

Number of ground frosts:

Number of air frosts: 2

Mean soil temperature at 30cm depth: 11.2

Mean soil temperature at 100cm depth: 9.9

Rainfall
(all totals in millimetres; all averages 1961 – 1990)

Total for the month: 64.8
Difference from average: +12.6

Percentage of the average: 124%

Wettest day: 20.8 (10th)

Number of rain days (>0.25mm): 14

Number of wet days (=> 1mm): 11

3-month total rainfall to 31st May: 214.2
Difference from average: +42.2

6-month rainfall total to 31st May: 312.2
Difference from average: -34.0

12-month rainfall total to 31st May: 657.6
Difference from average: +8.6

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 81%

Sunshine
(all averages 1961 – 1990)

Total for the month: 149.6 hours
Difference from average: -18.8

Percentage of the average: 89%

Mean daily sunshine: 4.8 hours
Difference from average: -0.6

Sunniest day: 11.5 hours (22nd)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 588.3 hours
Difference from average: +62.0

ISSN1350-483

Comments on May 2012
May was a month of “thirds” – two thirds cold and one third hot! The earlier part of the month was disappointing, including 6 days when the maximum stayed below 10°C. However, the maximum exceeded 20°C each day between the 22nd and the 29th, with an absolute maximum on 25.2°C on the 28th – the 4th highest absolute maximum for the month of May since 1962. Overall, May was above average for mean air temperature but not noticeably so, (some) warmer days being offset by cool nights. Rainfall was above average but the 6-month total still remains below normal. There was less bright sunshine than usual for May. This was the 9th year since 1882 when the number of hours of bright sunshine in March exceeded that for May; the last time this happened was in 2003.

Professor Tim Burt
Department of Geography
Durham University