May 2013

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

Mean daily maximum: 14.6
Difference from average: +0.3

Mean daily minimum: 5.5
Difference from average: -0.1

Mean air temperature: 10.1
Difference from average: +0.2

Absolute maximum: 22.8 (31st)

Absolute minimum: 2.0 (23rd)

Mean grass minimum: 2.6

Absolute grass minimum: -1.6 (25th)

Number of ground frosts: 6

Number of air frosts: 0

Mean soil temperature at 30cm depth: 10.7

Mean soil temperature at 100cm depth: 9.3

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

Total for the month: 100.8
Difference from average: +48.6

Percentage of the average: 193%

Wettest day: 40.8 (18th)

Number of rain days (>0.25mm): 15

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

3-month total rainfall to 31st May: 183.0
Difference from average: +32.6

6-month rainfall total to 31st May: 398.0
Difference from average: +89.5

12-month rainfall total to 31st May: 1068.2
Difference from average: +419.2

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 76%

Sunshine
(all averages 1961 – 1990)

Total for the month: 144.6 hours
Difference from average: -23.9

Percentage of the average: 86%

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

Sunniest day: 11.6 hours (25th)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 474.1 hours
Difference from average: -28.3

ISSN1350-483

Comments on May 2013
May felt disappointing although in fact mean air temperature was just a little above average; daytime temperatures were just a little above average and night-time temperatures just a little below. There was the same number of ground frosts as last year. Rainfall was well above average so that the running 12-month total remains above 1000mm for the 6th month in a row, a remarkable sequence. There were heavy falls on the 15th (21.4mm) and especially on the 18th (40.8mm); the latter caused extensive flooding in the Durham area. Rainfall intensity was extraordinary on the morning of the 18th with 12.2mm in the hour 08:00 – 09:00 (BST) and 10.2mm the next hour!

Hours of bright sunshine were less than average so that the accumulated total also remains well below average for the year so far.

Professor Tim Burt
Department of Geography
Durham University