July 2015

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

Mean daily maximum: 18.5
Difference from average: -0.8

Mean daily minimum: 9.9
Difference from average: -0.5

Mean air temperature: 14.2
Difference from average: -0.7

Absolute maximum: 30.2 (1st)

Absolute minimum: 5.0 (26th)

Mean grass minimum: 8.0

Absolute grass minimum: 2.8 (9th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.1

Mean soil temperature at 100cm depth: 14.2

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

Total for the month: 87.2
Difference from average: +35.6

Percentage of the average: 170%

Wettest day: 14.2 (4th)

Number of rain days (>0.25mm): 21

Number of wet days (=> 1mm): 16

3-month total rainfall to 31st July: 553.4
Difference from average: +21.8

6-month rainfall total to 31st July: 277.7
Difference from average: -68.5

12-month rainfall total to 31st July: 193.8
Difference from average: -95.6

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: 80%

Sunshine
(all averages 1961 – 1990)

Total for the month: 120.9 hours
Difference from average: -34.0

Percentage of the average: 78%

Mean daily sunshine: 3.9 hours
Difference from average: -1.1

Sunniest day: 12.4 hours (1st)

Number of days with no recorded sunshine: 2

Cumulative total sunshine since 1st January: 894.1 hours
Difference from average: 49.2

ISSN1350-483

Comments on July 2015
July was a disappointing month, the second month in a row with below-average temperatures. And it started so well, with a maximum over 30°C on the 1st!  This was the warmest July day in Durham since 2006 and one of the very few ever to exceed 30°C at Durham. Since 1st January 1850, only 30 days have reached a maximum of 30°C; 1st July 2015 is the 21st warmest day on record at Durham (equal to 15th August 1893). The warmest day on record is 16th July 1876: 33.6°C.

All that said, mean air temperature in July was the lowest since 2000, the 44th equal lowest since 1850, only just above the lowest quartile. The mean maximum was the lowest since 2012 and the mean minimum the lowest since 2011. The 12-month mean air temperature is now down to 9.3°C having been just above 10°C in January.

Rainfall was well above average but again it was only the worst July since the very poor summer of 2012. Even with an extra day, there was less sunshine in July than in June. Since 1882, there have been 54 years when July was less sunny than June (n = 134).

Professor Tim Burt
Department of Geography
Durham University