May 2018

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

Mean daily maximum: 17.4
Difference from average: +3.1

Mean daily minimum: 6.8
Difference from average: +1.2

Mean air temperature: 12.1
Difference from average: +2.2

Absolute maximum: 26.7 (7th)

Absolute minimum: 0.9 (18th)

Mean grass minimum: 4.7

Absolute grass minimum: -1.1 (18th)

Mean concrete minimum: 8.4

Absolute concrete minimum: 2.0 (1st)

Number of ground frosts: 2

Number of air frosts: 0

Mean soil temperature at 30cm depth: 13.0

Mean soil temperature at 100cm depth: 10.2

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

Total for the month: 24.4
Difference from average: -27.8

Percentage of the average: 47%

Wettest day: 7.8 (12th)

Number of rain days (>0.25mm): 7

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

3-month total rainfall to 31st May: 187.8
Difference from average: +15.8

6-month rainfall total to 31st May: 324.2
Difference from average: -22.0

12-month rainfall total to 31st May: 742.8
Difference from average: +93.8

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: %

Sunshine
(all averages 1961 – 1990)

Total for the month: 241.7 hours
Difference from average: +73.2

Percentage of the average: 143%

Mean daily sunshine: 7.8 hours
Difference from average: +2.4

Sunniest day: 15.0 hours (14th)

Number of days with no recorded sunshine: 0

Cumulative total sunshine since 1st January: 552.3 hours
Difference from average: +26.0

ISSN1350-483

Comments on May 2018
Problems with the phone line lasted throughout May with just a small section of data for the 17th and 18th. Once again, I have estimated missing data using a combination of the Department of Geography‘s weather station and Ken Cook’s records from Copley. Given that the May record for the Durham Observatory is almost entirely absent, these results must be treated with extreme caution, although the results do look close to Met Office regional averages.

May was a very warm month, daytime temperatures in particular. Mean air temperature is the third equal warmest, beaten only by last year and 1952. The mean maximum temperature is the highest on record for May, equal to 1952.

April was a dry month, but not unusually so. The total ranks only 41st lowest since 1850.
It was the 4th sunniest May since 1881, the sunniest May in Durham since 1989.

Emeritus Professor Tim Burt
Department of Geography
Durham University