September 2006

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

Mean daily maximum: 20.2
Difference from average: +3.5

Mean daily minimum: 11.8
Difference from average: +3.1

Mean air temperature: 16.0
Difference from average: +3.2

Absolute maximum: 26.7 (21st)

Absolute minimum: 4.1 (7th)

Mean grass minimum: 9.3

Absolute grass minimum: 1.8 (7th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.3

Mean soil temperature at 100cm depth: 15.5

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

Total for the month: 32.4
Difference from average: -23.2

Percentage of the average: 58%

Wettest day: 7.8 (2nd)

Number of rain days (>0.25mm): 10

Number of wet days (=> 1mm): 8

3-month total rainfall to 30th September: 98
Difference from average: -76.2

6-month rainfall total to 30th September: 240.1
Difference from average: -85.2

12-month rainfall total to 30th September: 529.7
Difference from average: -119.3

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 84%

Sunshine
(all averages 1961 – 1990)

Total for the month: 125.8 hours
Difference from average: +1.8

Percentage of the average: 101.5%

Mean daily sunshine: 4.2 hours
Difference from average: +0.1

Sunniest day: 10.2 hours (7th)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 1124.4 hours
Difference from average: +14.9

Wind

The mean wind speed: 11.1km/h [6.0kt]
Difference from average: -1.1km/hr

The highest gust: 64.8km/h [35kt] from 249° at 12:45 GMT on 2nd

ISSN1350-483

Comments on September 2006
Following a record-breaking July, this was the warmest September on record at Durham since records began in 1850, beating the previous record (1949) by a massive margin of 0.7°C. It was also the first time since 1956 when September has been warmer than August (This has only happened 5 times since 1850 including this year). I only have records of mean maximum and mean minimum to hand since 1950, but from these records it is clear that both were records for September, as might be expected given the overall mean, with the mean maximum exceeding 20°C for the first time. The absolute maximum of 26.7°C is also a record (since 1950).

For the 7th month out of 9 this year, rainfall was below average, and all long-term totals are now well below average. Sunshine was about average for the time of years but it was nevertheless a much sunnier month than August.

Professor Tim Burt
Department of Geography
Durham University