May 2011

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

Mean daily maximum: 16.0
Difference from average: +1.7

Mean daily minimum: 7.4
Difference from average: +1.8

Mean air temperature: 11.7
Difference from average: +1.8

Absolute maximum: 20.0 (7th)

Absolute minimum: -0.8 (4th)

Mean grass minimum: 5.1

Absolute grass minimum: -4.0 (4th)

Number of ground frosts: 3

Number of air frosts: 1

Mean soil temperature at 30cm depth: 12.8

Mean soil temperature at 100cm depth: 12.2

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

Total for the month: 32.6
Difference from average: -19.2

Percentage of the average: 63%

Wettest day: 11.8 (26th)

Number of rain days (>0.25mm): 12

Number of wet days (=> 1mm): 7

3-month total rainfall to 31st May: 64.6
Difference from average: -85.8

6-month rainfall total to 31st May: 2282.0
Difference from average: -80.3

12-month rainfall total to 31st May:
Difference from average: +35.4

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 70%

Sunshine
(all averages 1961 – 1990)

Total for the month: 165.3 hours
Difference from average: -3.2

Percentage of the average: 98.1%

Mean daily sunshine: 5.3 hours
Difference from average: -0.1

Sunniest day: 11.8 hours (1st)

Number of days with no recorded sunshine: 0

Cumulative total sunshine since 1st January: 679.4 hours
Difference from average: +153.1

Wind

The mast is still broken, we hope to replace it soon.

ISSN1350-483

Comments on May 2011
Although the mean maximum was lower than in April, overall, it was a warmer month than April, given higher night-time temperatures. It was the warmest May since 1998 (equal to 1999). Indeed, it was the 6th warmest may at Durham since 1850. The mean maximum was the highest since 2004 (19th equal highest since 1900), and the mean minimum was the highest since 2003 (5th highest on record since 1900). Not surprisingly, given the record-breaking April and a very warm may, this turned out to be the warmest spring on record at Durham since 1850, beating the previous record (2007) by 0.3°C. Interestingly, of the seven warmest springs on record at Durham, six have been since 2002, the exception being 1945.

May was the third below-average month for rainfall in a row, although only the driest May since 2009. Spring was very dry, the fifth driest on record since 1850, and the driest since 1956. The other drier springs were 1929, 1875 and 1858. Whilst not quite so extreme as places further south, Durham rainfall, as ever, has an “eastern” character, more like East Anglia than the Pennine hills! Despite the low rainfall and high temperatures, sunshine was just below average.

Professor Tim Burt
Department of Geography
Durham University