July 2017

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

Mean daily maximum: 18.8
Difference from average: -0.5

Mean daily minimum: 10.9
Difference from average: +0.5

Mean air temperature: 14.9
Difference from average: 0.0

Absolute maximum: 23.8 (17th)

Absolute minimum: 8.2 (8th)

Mean grass minimum: 9.2

Absolute grass minimum: 4.7 (8th)

Mean concrete minimum: 11.4

Absolute concrete minimum: 7.7 (8th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.4

Mean soil temperature at 100cm depth: 14.9

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

Total for the month: 71.2
Difference from average: +19.6

Percentage of the average: 138%

Wettest day: 13.2 (10th)

Number of rain days (>0.25mm): 16

Number of wet days (=> 1mm): 14

3-month total rainfall to 31st July: 194.4
Difference from average: +22.4

6-month rainfall total to 31st July: 347.2
Difference from average: +1.0

12-month rainfall total to 31st July: 678.3
Difference from average: +29.3

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: %

Sunshine
(all averages 1961 – 1990)

Total for the month: 111.7 hours
Difference from average: -43.2

Percentage of the average: 72%

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

Sunniest day: 10.9 hours (17th)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 806.2 hours
Difference from average: -387

ISSN1350-483

Comments on July 2017
Mean air temperature in July was exactly average, barely warmer than June, but only the coolest July since 2015. Daytime temperatures were disappointing but night-time temperatures above average. The 12-month average had reached 10°C in June but fell back to 9.95°C in July, but still one of the highest values on record: 35th highest in exactly 2000 averages).

July was another wet month, but not exceptionally so. All long-term averages are now slightly above average again. Not unexpectedly, sunshine was below average, the lowest July total since the wet summer of 2012. Curiously, March, April and May were all sunnier than June and July!

Professor Tim Burt
Department of Geography
Durham University