September 2020

Temperatures
(all temperatures in degrees Celsius; all averages 1961 – 2010)

Mean daily maximum: 17.2
Difference from average: 0.0

Mean daily minimum: 8.8
Difference from average: –0.2

Mean air temperature: 13.0
Difference from average: -0.1

Absolute maximum: 26.4 (15th)

Absolute minimum: 1.8 (28th)

Mean grass minimum: 6.9

Absolute grass minimum: -0.9 (28th)

Mean concrete minimum: 6.6

Absolute concrete minimum: -0.5 (28th)

Number of ground frosts: 1

Number of air frosts: 0

Mean soil temperature at 30cm depth: 15.7

Mean soil temperature at 100cm depth: 14.6

Rainfall
(all totals in millimetres; all averages 1961 – 2010)

Total for the month: 57.0
Difference from average: +3.2

Percentage of the average: 106%

Wettest day: 20.2 (23rd)

Number of rain days (>0.2mm): 15

Number of wet days (=>1.0mm): 8

3-month total rainfall to 30th September: 223.4
Difference from average: +51.4

6-month rainfall total to 30th September: 327.8
Difference from average: -18.4

12-month rainfall total to 30th September: 702.4
Difference from average: +53.4

Sunshine
(all averages 1961 – 1990)

Total for the month: 148.6 hours
Difference from average: +16.6

Percentage of the average: 113%

Mean daily sunshine: 5.0 hours
Difference from average: +0.6

Sunniest day: 8.4 hours (14th)

Number of days with no recorded sunshine: 2

Cumulative sunshine since 1st January: 1358.5
Difference from average: +143.5

Note: the monthly sunshine total is now calculated from the UKMO E&NE regional total.
Daily sunshine totals quoted here and in the data summary are uncorrected.

Wind
(all data from West Building roof, Lower Mountjoy)

Average wind speed: 5.7kph

Maximum gust: 69.2kph (13:45, 25th, NE)

ISSN1350-483

Comments on September 2020
Mean air temperature was just below average with mean maximum exactly average and mean minimum 0.2°C below average. Notwithstanding this ‘average’ weather, Durham experienced its 10th hottest September day since 1900 on the 15th with a maximum of 26.4°C. The minimum temperature on the 8th is the 44th equal highest for September since 1900. There were some disappointingly cool days towards the end of the month with the maximum of 10.1°C on the 24th being the 18th equal coldest September day since 1900.

The rainfall was more or less average too. The daily total of 20.2mm on the 23rd is the 58th wettest September day since 1850. The 3-month and 12-month totals remain well above average, but the 6-month total is a little below average, given the dry latter part of spring.

Sunshine was above average, the 31st sunniest September since 1882, just into the upper quartile.

There was a gust of 69.2kph (measured at  the West Building on the Lower Mountjoy campus) at 13:45 in the 25th, a period of very strong winds from the NE around a deep low in the southern North Sea.

Emeritus Professor Tim Burt
Department of Geography
Durham University