May 2010

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

Mean daily maximum: 15.0
Difference from average: +0.7

Mean daily minimum: 4.6
Difference from average: -1.0

Mean air temperature: 9.8
Difference from average: -0.1

Absolute maximum: 27.2 (23rd)

Absolute minimum: -2.5 (12th)

Mean grass minimum: 1.9

Absolute grass minimum: -6.2 (12th)

Number of ground frosts: 11

Number of air frosts: 2

Mean soil temperature at 30cm depth: 12.6

Mean soil temperature at 100cm depth: 11.5

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

Total for the month: 22.8
Difference from average: -29.0

Percentage of the average: 44%

Wettest day: 8.6 (6th)

Number of rain days (>0.25mm): 11

Number of wet days (=> 1mm):

3-month total rainfall to 31st May: 103.6
Difference from average: -46.8

6-month rainfall total to 31st May: 314.4
Difference from average: +5.9

12-month rainfall total to 31st May: 808.8
Difference from average: +159.8

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 74%

Sunshine
(all averages 1961 – 1990)

Total for the month: 146.3 hours
Difference from average: -22.2

Percentage of the average: 87%

Mean daily sunshine: 4.7 hours
Difference from average: -0.7

Sunniest day: 9.93 hours (18th)

Number of days with no recorded sunshine: 0

Cumulative total sunshine since 1st January: 527.1 hours
Difference from average: +0.8

Wind

The anemometer remains problematic, no summary results can be provided.

ISSN1350-483

Comments on May 2010
Despite having the warmest day in May since 2001, May was nevertheless a disappointing month. Daytime temperatures were above average but night-time temperatures well below and overall, mean air temperature was just a little below average. There was a short spell of very warm days from the 20th to the 23rd but otherwise daytime temperatures were poor with a maximum of only 9.9°C on the 2nd. There was the highest number of ground frosts since 1997. The 12-month running mean remains at its lowest value since 2001.

May was a dry month contributing to a dry spring. It was the 46th driest spring in 161 years, not exceptional therefore but sufficiently low to begin worries about summer drought perhaps. The 3-month rainfall total is well below average and the 6-month total is almost exactly average, whereas the 12-month total remain well above average.

Professor Tim Burt
Department of Geography
Durham University