August 2009

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

Mean daily maximum: 20.1
Difference from average: +1.0

Mean daily minimum: 11.5
Difference from average: +1.2

Mean air temperature: 15.8
Difference from average: +1.1

Absolute maximum: 24.4 (19th)

Absolute minimum: 8.9 (26th)

Mean grass minimum: 8.5

Absolute grass minimum: 4.8 (25th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.7

Mean soil temperature at 100cm depth: 15.9

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

Total for the month: 39.2
Difference from average: -27.9

Percentage of the average: 58%

Wettest day: 12.0 (31st)

Number of rain days (>0.25mm): 14

Number of wet days (=> 1mm): 9

3-month total rainfall to 31st August: 287.2
Difference from average: +116.8

6-month rainfall total to 31st August: 383.3
Difference from average: +62.5

12-month rainfall total to 31st August: 719.5
Difference from average: +70.5

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 80%

Sunshine
(all averages 1961 – 1990)

Total for the month: 129.2 hours
Difference from average: -26.1

Percentage of the average: 83%

Mean daily sunshine: 4.2 hours
Difference from average: -0.8

Sunniest day: 9.5 hours (8th)

Number of days with no recorded sunshine: 0

Cumulative total sunshine since 1st January: 1057.6 hours
Difference from average: +57.1

Wind

The mean wind speed: 14.1km/h [7.6kt]
Difference from average: +2.6km/hr

The highest gust: 72km/h [38.9kt] from 187° at 15:22 GMT on 19th

ISSN1350-483

Comments on August 2009
It was the warmest August since 2003, and the equal 22nd warmest since 1850. Minimum temperatures were a little higher above average than maximum temperatures. The mean air temperature for the summer as a whole was the same as last year, 14.9°C, equal 30th warmest since 1850.

August was a dry month, equal 53rd driest since 1850. Nevertheless, it was the 11th wettest summer on record since 1850. When we note that 2008 was the 8th wettest and 2007 was the 14th wettest, the last three summers have been disappointingly wet therefore! These are the three wettest summers in a row at Durham since records began in 1850. 2004 was the 10th wettest summer too. This decade has therefore seen a complete reversal of the very dry summers of the 1990s.

Professor Tim Burt
Department of Geography
Durham University