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September 2009

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

Mean daily maximum: 18.0
Difference from average: +1.3

Mean daily minimum: 9.2
Difference from average: +0.5

Mean air temperature: 13.6
Difference from average: +0.9

Absolute maximum: 23.7 (12th)

Absolute minimum: 4.8 (18th)

Mean grass minimum: 6.4

Absolute grass minimum: 1.9 (20th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth:

Mean soil temperature at 100cm depth:

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

Total for the month: 14.4
Difference from average: -41.2

Percentage of the average: 26%

Wettest day: 5.6 (2nd)

Number of rain days (>0.25mm): 8

Number of wet days (=> 1mm): 4

3-month total rainfall to 30th September: 221
Difference from average: -20.8

6-month rainfall total to 30th September: 376.6
Difference from average: +51.3

12-month rainfall total to 30th September: 628.2
Difference from average: +46.8

(Averages for 09:00 hours GMT)

Relative Humidity:

(all averages 1961 – 1990)

Total for the month: 106.4 hours
Difference from average: -17.6

Percentage of the average: 86%

Mean daily sunshine: 3.5 hours
Difference from average: -0.6

Sunniest day: 10.2 hours (12th)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 1164 hours
Difference from average: +39.6


The mean wind speed: 10.9km/h [5.9kt]
Difference from average: -1.3km/hr

The highest gust: 78.7km/h [42.5kt] from 183° at 10:41 GMT on 8th


Comments on September 2009
September temperatures were well above average, especially during the day. It was the 23rd equal warmest in 160 years and included the highest September temperature since 2004 (23.7°C on the 12th). It was the 12th driest September since 1850 with the fewest number of rain days (with 2003) since records began in 1950. Nevertheless, it was a little sunny than normal.

Professor Tim Burt
Department of Geography
Durham University