July 2018

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

Mean daily maximum: 22.5
Difference from average: +3.2

Mean daily minimum: 12.0
Difference from average: +1.6

Mean air temperature: 17.3
Difference from average: +2.5

Absolute maximum: 26.7 (26th)

Absolute minimum: 7.1 (18th)

Mean grass minimum: 10.0

Absolute grass minimum: 3.3 (18th)

Mean concrete minimum: 13.6

Absolute concrete minimum: 8.9 (18th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 19.0

Mean soil temperature at 100cm depth: 16.6

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

Total for the month: 56.0
Difference from average: +4.4

Percentage of the average: 109%

Wettest day: 27.6 (16th)

Number of rain days (>0.25mm): 9

Number of wet days (=> 1mm): 6

3-month total rainfall to 31st July: 114.2
Difference from average: -57.8

6-month rainfall total to 31st July: 313.6
Difference from average: -32.6

12-month rainfall total to 31st July: 655.0
Difference from average: +6.0

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: 76%

Sunshine
(all averages 1961 – 1990)

Total for the month: 185.3 hours
Difference from average: +30.4

Percentage of the average: 120%

Mean daily sunshine: 6.0 hours
Difference from average: +0.5

Sunniest day: 15.5 hours (14th)

Number of days with no recorded sunshine: 0

Cumulative total sunshine since 1st January: 889.4 hours
Difference from average: +44.5

ISSN1350-483

Comments on July 2018
This was the 7th warmest July since 1850, the warmest since 2013; 2006 is the record holder (18.4°C). Daytime temperatures were particularly high with the equal 4th highest mean maximum since 1900. There were 8 days with a maximum above 25°C, again the 4th equal highest total for July, but not quite the 26 days above 25°C experienced at Oxford! It would have been a very dry July too, but for the fall of 27.6mm on 16th, the wettest day of the year so far. There was heavy rain late in the evening with 8mm in the 15 minutes to 22:00 hours and a total of 12.8mm in the hour 21:30 – 22:30, a very high hourly intensity indeed. There were only 9 rain days and only 6 days with totals above 1mm. It was not a particularly sunny month, only the 31st sunniest since 1882.

Once again, we had problems with the phone line (13th – 25th), so this report uses data from the AWS on the West building roof plus Ken Cook’s data from Copley to infill the gaps.

Emeritus Professor Tim Burt
Department of Geography
Durham University