September 2019

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

Mean daily maximum: 17.6
Difference from average: +0.4

Mean daily minimum: 9.1
Difference from average: +0.4

Mean air temperature: 13.3
Difference from average: +0.2

Absolute maximum: 22.7 (21st)

Absolute minimum: 2.0 (7th)

Mean grass minimum: 7.2

Absolute grass minimum: -0.1 (7th)

Mean concrete minimum: 8.8

Absolute concrete minimum: 3.0 (7th)

Number of ground frosts: 1

Number of air frosts: 0

Mean soil temperature at 30cm depth: 15.2

Mean soil temperature at 100cm depth: 15.1

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

Total for the month: 84.2
Difference from average: +28.8

Percentage of the average: 152%

Wettest day: 21.4 (30th)

Number of rain days (>0.25mm): 19

Number of wet days (=> 1mm): 10

3-month total rainfall to 30th September: 234.6
Difference from average: +62.6

6-month rainfall total to 30th September: 411.2
Difference from average: +65

12-month rainfall total to 30th September: 663
Difference from average: +14

Sunshine
(all averages 1961 – 1990)

Total for the month: 108.4 hours
Difference from average: -15.2

Percentage of the average: 88%

Mean daily sunshine: 3.6 hours
Difference from average: -0.5

Sunniest day: 8.6 hours (19th)

Number of days with no recorded sunshine: 2

Cumulative total sunshine since 1st January: 1044.2 hours
Difference from average: -118.6

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

Average wind speed: 4.9kph

Maximum gust: 54.7kph (14:45, 12th, W)

ISSN1350-483

Comments on September 2019
September was warmer than average but not greatly so: both the mean maximum and mean minimum were 0.4°C above average and mean air temperature just 0.2°C above average. There was some variety of daytime temperature with a maximum of just 13.6°C on 9th yet three days into the twenties later in the month: 21.8°C on 19th, 22.2°C on 20th and 22.7°C on 21st. It was a wet month, with the wettest day being the last day of the month. Heavy rain had been forecast for Freshers’ Sunday’ (29th) so perhaps it was with some relief that the rain held off until the next day, a total fall of 21.4mm. Yet again, sunshine was below average. The sunniest day was 19th, also one of the warmest, some very welcome ‘Indian summer’ weather!

Emeritus Professor Tim Burt
Department of Geography
Durham University