September 2011

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

Mean daily maximum: 18.1
Difference from average: +1.4

Mean daily minimum: 10.0
Difference from average: +1.3

Mean air temperature: 14.1
Difference from average: +1.4

Absolute maximum: 24.8 (30th)

Absolute minimum: 4.4 (15th)

Mean grass minimum: 8.1

Absolute grass minimum: 2.1 (15th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth:

Mean soil temperature at 100cm depth:

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

Total for the month: 28.4
Difference from average: -27.2

Percentage of the average: 51%

Wettest day: 6.0 (6th)

Number of rain days (>0.25mm): 11

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

3-month total rainfall to 30th September: 245.8
Difference from average: +71.6

6-month rainfall total to 30th September: 333.8
Difference from average: +8.5

12-month rainfall total to 30th September: 720.2
Difference from average: +71.2

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 82%

Sunshine
(all averages 1961 – 1990)

Total for the month: 119.4 hours
Difference from average: -4.6

Percentage of the average: 96%

Mean daily sunshine: 3.9 hours
Difference from average: -0.2

Sunniest day: 8.2 hours (29th)

Number of days with no recorded sunshine: 1 (16th)

Cumulative total sunshine since 1st January: 1156.5 hours
Difference from average: +32.1

Wind

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

ISSN1350-483

Comments on September 2011
Remarkably, the last three days all exceeded 24°C but, unlike other places in the UK, these were not record-breaking maximum temperatures at Durham for September. Otherwise, it was not particularly notable for temperatures with some cooler days in the latter half of the month before the heat wave at the end. It ended up being the 9th equal warmest September since 1850, the warmest since 2006 (which is the warmest September on record at Durham with a record maximum of 26.7°C in the 21st).

It was the driest September since 2004. Nevertheless, all long-period cumulative totals remain above average, although the 6-month total is only just so.

It was the sunniest September since 2006 but even so still a little below average.

Professor Tim Burt
Department of Geography
Durham University