May 2015

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

Mean daily maximum: 13.8
Difference from average: -0.5

Mean daily minimum: 6.0
Difference from average: +0.4

Mean air temperature: 9.9
Difference from average: 0.0

Absolute maximum: 18.1 (23rd)

Absolute minimum: -1.0 (1st)

Mean grass minimum: 4.3

Absolute grass minimum: -3.0 (1st)

Number of ground frosts: 1

Number of air frosts: 1

Mean soil temperature at 30cm depth: 11.6

Mean soil temperature at 100cm depth: 10.5

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

Total for the month: 71.8
Difference from average: +19.6

Percentage of the average: 138%

Wettest day: 12.8 (5th)

Number of rain days (>0.25mm): 15

Number of wet days (=> 1mm): 12

3-month total rainfall to 31st May: 140.1
Difference from average: -31.9

6-month rainfall total to 31st May: 231.4
Difference from average: -114.8

12-month rainfall total to 31st May: 541.2
Difference from average: -107.8

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: 73%

Sunshine
(all averages 1961 – 1990)

Total for the month: 147.2 hours
Difference from average: -21.3

Percentage of the average: 87%

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

Sunniest day: 10.4 hours (1st)

Number of days with no recorded sunshine: 0

Cumulative total sunshine since 1st January: 634.5 hours
Difference from average: +108.2

ISSN1350-483

Comments on May 2015
May was a disappointing month, the mean air temperature being exactly average, but it was only the coolest May since 2010. There was the lowest mean maximum since 1996, the 35th equal lowest since 1900. The mean minimum was above average. Rainfall was a little above average but all long-term totals remain below average. There was one spectacular downpour on the afternoon of the 19th; only 4.6mm was recorded (hour ending 1500 BST) but it fell in no more than 15 minutes, so the intensity was spectacular, Durham was awash and your correspondent soaked! The amount of sunshine was disappointing, less than in April; however, the cumulative total remains well above average for the year as a whole.

Professor Tim Burt
Department of Geography
Durham University