August 2017

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

Mean daily maximum: 18.6
Difference from average: -0.5

Mean daily minimum: 10.6
Difference from average: +0.2

Mean air temperature: 14.6
Difference from average: -0.1

Absolute maximum: 21.8 (17th)

Absolute minimum: 6.1 (21st)

Mean grass minimum: 8.2

Absolute grass minimum: 4.4 (21st)

Mean concrete minimum: 10.2

Absolute concrete minimum: 6.3 (21st)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.2

Mean soil temperature at 100cm depth: 15.1

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

Total for the month: 50.0
Difference from average: -17.1

Percentage of the average: 75%

Wettest day: 18.4 (8th)

Number of rain days (>0.25mm): 15

Number of wet days (=> 1mm): 12

3-month total rainfall to 31st August: 224.6
Difference from average: +52.6

6-month rainfall total to 31st August: 315.8
Difference from average: -30.4

12-month rainfall total to 31st August: 658.5
Difference from average: 9.5

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: 79%

Sunshine
(all averages 1961 – 1990)

Total for the month: 110.7 hours
Difference from average: -44.8

Percentage of the average: 71%

Mean daily sunshine: 3.6 hours
Difference from average: -1.4

Sunniest day: 9.4 hours

Number of days with no recorded sunshine*: 4

Cumulative total sunshine since 1st January: 916.9 hours
Difference from average: -83.6

*Provisional data – data issued on 31st

ISSN1350-483

Comments on August 2017
August was the first month since November 2016 to have below-average mean air temperature. Daytime maximum temperatures were disappointing but night-time minima were above average. Rainfall was below average although measurable rain fell on half the days. In terms of bright sunshine, it was another disappointing month, the 18th lowest August total since 1882.

Overall, summer was only marginally cooler than last year, but still ranking equal 38th highest in 168 years. Only above-average minima kept the overall mean air temperature at this relatively tolerable level. It was a wet summer, with the 135th highest total in 168 years. Summer sunshine was in short supply: the 3rd lowest August total on record. Using the Davis (1968) index of summer weather (which is based on mean air temperature, total rainfall and hours of sunshine), this was the 24th worst summer since 1900 (equal with 2015), not nearly as bad as 2012 but reflecting a general deterioration in Durham summers since the mid-1990s.

Emeritus Professor Tim Burt
Department of Geography
Durham University