August 2011

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

Mean daily maximum: 18.7
Difference from average: -0.4

Mean daily minimum: 10.3
Difference from average: -0.1

Mean air temperature: 14.5
Difference from average: -0.2

Absolute maximum: 23.2 (1st)

Absolute minimum: 7.5 (10th)

Mean grass minimum: 8.3

Absolute grass minimum: 4.7 (10th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.5

Mean soil temperature at 100cm depth: 15.3

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

Total for the month: 130.8
Difference from average: +63.7

Percentage of the average: 195%

Wettest day: 36.2 (6th)

Number of rain days (>0.25mm): 22

Number of wet days (=> 1mm): 19

3-month total rainfall to 31st August: 265.6
Difference from average: +95.2

6-month rainfall total to 31st August: 330.2
Difference from average: +9.4

12-month rainfall total to 31st August: 767.2
Difference from average: +118.2

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 84%

Sunshine
(all averages 1961 – 1990)

Total for the month: 99.4 hours
Difference from average: -56.1

Percentage of the average: 64%

Mean daily sunshine: 3.2 hours
Difference from average: -1.8

Sunniest day: 7.4 hours (23rd)

Number of days with no recorded sunshine: 0

Cumulative total sunshine since 1st January: 1037.1 hours
Difference from average: +36.6

Wind

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

ISSN1350-483

Comments on August 2011
Day-time temperatures were well below average in August, and night-time temperatures a little below average so that, for the second month in a row, mean air temperature was below average. Actually, it was 0.1°C warmer than August last year! Both the mean maximum and mean minimum were the same as 1998 and the lowest since 1994. August had well above average rainfall, the wettest since 2004. The number of rain days was the highest since 1985.

For the 4th month in a row, sunshine was below average, but only the dullest August since 2006. Overall, it was the sixth worst August for hours of bright sunshine since 1882 (but still rather better than the meagre 57 hours in 1912).

Comments on Summer 2011
The mean air temperature for the summer was 14.1°C, 0.1°C below average. This is the same average as summer 1998 and the coldest since 1993 – exactly the same statistic that has been reported nationally. This is only just below the long-term average, of course, but disappointing in relation to recent summers.

It was the 14th wettest summer on record at Durham since 1850, drier than 2008 and 2009 but wetter than 2007. The last five summers taken together, have been the 2nd wettest sequence on record; only 1927-1931 was an even worse run of summers in terms of rainfall.

This was the 5th lowest amount of sunshine in summer since 1882, the worst since 1986.

Using the Davis Index of summer weather, which weights average temperature, rainfall and sunshine, 2011 ranks as the 12th worst summer at Durham since 1886, marginally poorer than 2007 and the worst since 1987. Taken together, the last five summers have been on average the 4th worst series on record.

Disappointing indeed!

Professor Tim Burt
Department of Geography
Durham University