April 2018

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

Mean daily maximum: 11.7
Difference from average: +0.7

Mean daily minimum: 5.1
Difference from average: +2.0

Mean air temperature: 8.4
Difference from average: +1.4

Absolute maximum: 23.1 (19th)

Absolute minimum: -0.8 (5th)

Mean grass minimum: 3.3

Absolute grass minimum: -3.0 (5th)

Mean concrete minimum: 4.6

Absolute concrete minimum: -1.7 (5th)

Number of ground frosts: 5

Number of air frosts: 1

Mean soil temperature at 30cm depth: 8.5

Mean soil temperature at 100cm depth: 7.3

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

Total for the month: 74.0
Difference from average: +27.6

Percentage of the average: 156%

Wettest day: 23.4 (4th)

Number of rain days (>0.25mm): 14

Number of wet days (=> 1mm): 9

3-month total rainfall to 30th April: 199.4
Difference from average: +27.4

6-month rainfall total to 30th April: 372.8
Difference from average: +26.6

12-month rainfall total to 30th April: 735.2
Difference from average: +86.2

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: 84%

Sunshine
(all averages 1961 – 1990)

Total for the month: 112.2 hours
Difference from average: -21.0

Percentage of the average: 84%

Mean daily sunshine: 3.7 hours
Difference from average: -0.7

Sunniest day: 11.1 hours (19th)

Number of days with no recorded sunshine: 5

Cumulative total sunshine since 1st January: 310.6 hours
Difference from average: -47.2

ISSN1350-483

Comments on April 2018
The beginning of our problems with a faulty phone line began on 23rd April. I have estimated missing values using either the Department of Geographys weather station on the roof of the West Building on the main campus or from Ken Cook’s record at Copley (for which many thanks, Ken). Any conclusions must be tentative therefore.

April was just 0.1°C cooler than last year, ranking equal 23rd warmest since 1850. Minimum temperatures were notably high, the 6th highest average for April on record. April was a wet month, the 23rd wettest April on record but still less than half the record breaker in April 1989 (151mm). April was a dull month, ranking 101st least sunny out of a total of 134, in the lowest quartile therefore.

Emeritus Professor Tim Burt
Department of Geography
Durham University