September 2013

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

Mean daily maximum: 17.1
Difference from average: +0.4

Mean daily minimum: 8.4
Difference from average: -0.3

Mean air temperature: 12.8
Difference from average: +0.1

Absolute maximum: 24.0 (5th)

Absolute minimum: 3.4 (8th)

Mean grass minimum: 5.7

Absolute grass minimum: -0.2 (8th)

Number of ground frosts: 1

Number of air frosts: 0

Mean soil temperature at 30cm depth: 14.9

Mean soil temperature at 100cm depth: 14.9

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

Total for the month: 84.6
Difference from average: +29.0

Percentage of the average: 152%

Wettest day: 63 (6th)

Number of rain days (>0.25mm): 9

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

3-month total rainfall to 30th September: 208.4
Difference from average: +34.2

6-month rainfall total to 30th September: 370.4
Difference from average: +45.1

12-month rainfall total to 30th September: 852.6
Difference from average: +203.6

Humidity
(Averages for 09:00 hours GMT)

Relative Humidity: 83%

Sunshine
(all averages 1961 – 1990)

Total for the month: 98.9 hours
Difference from average: -25.1

Percentage of the average: 80%

Mean daily sunshine: 3.3 hours
Difference from average: -0.8

Sunniest day: 8.4 hours (23rd)

Number of days with no recorded sunshine: 2

Cumulative total sunshine since 1st January: 1023.2 hours
Difference from average: -101.2

ISSN1350-483

Comments on September 2013
As a whole September was just above average temperature; it felt warmer because of warmer than average days but minimum temperatures were below average and there was an early ground frost on the 8th.

September would have been a dry month – only 9 rain days – but for the exceptional total on the 6th when 63mm fell in 18 hours. Hourly totals of 6, 12 and 9mm during the evening are exceptional. This is the 10th wettest day in Durham since 1850 and the highest total since 17th July 2009 when 64.2mm was recorded.

September was another dull month and cumulative sunshine hours for the year remain well below average.

Professor Tim Burt
Department of Geography
Durham University