April 2020

Temperatures
(all temperatures in degrees Celsius; all averages 1961 – 2010)

Mean daily maximum: 14.4
Difference from average: +2.5

Mean daily minimum: 4.4
Difference from average: +0.7

Mean air temperature: 9.4
Difference from average: +1.6

Absolute maximum: 21.2 (15th)

Absolute minimum: -2.3 (14th)

Mean grass minimum: 2.3

Absolute grass minimum: -5.3 (14th)

Mean concrete minimum: 4.5

Absolute concrete minimum: -1.9 (14th)

Number of ground frosts: 7

Number of air frosts: 1

Mean soil temperature at 30cm depth: 10.5

Mean soil temperature at 100cm depth: 9.0

Rainfall
(all totals in millimetres; all averages 1961 – 2010)

Total for the month: 3.8
Difference from average: -47.6

Percentage of the average: 7%

Wettest day: 1.8 (29th)

Number of rain days (>0.2mm): 5

Number of wet days (=>1.0mm): 1

3-month total rainfall to 30th April: 117.6
Difference from average: -54.4

6-month rainfall total to 30th April: 290.0
Difference from average: -56.2

12-month rainfall total to 30th April: 760.6
Difference from average: 111.6

Sunshine
(all averages 1961 – 1990)

Total for the month: 169.5 hours
Difference from average: +30.2

Percentage of the average: 122%

Mean daily sunshine: 5.7 hours
Difference from average: +1.1

Sunniest day: 10.5 hours (7th, 15th)

Number of days with no recorded sunshine: 0

Cumulative sunshine since 1st January: 488.3
Difference from average: +96.0

Wind
(all data from West Building roof, Lower Mountjoy)

Average wind speed: 6.0kph

Maximum gust: 78.9kph (10:45, 2nd, W)

ISSN1350-483

Comments on April 2020
I
t looked for much of the month as if this might be the driest April on record at Durham, but 0.8mm on the 26th, 1.8mm on the 29th and 0.4mm on the 30th were added to earlier totals of 0.2mm (3rd) and 0.6mm (10th) to give the princely sum of 3.8mm for the whole month, falling on just five days. Only 1938 (2.2mm) and 1912 (2.4mm) have seen drier Aprils since 1850. Only four years have seen fewer rain days in April: 3 in 1912 and 4 in 1938, 1974 and 2011.

This was the 5th warmest April on record, the warmest April since the record holder in 2011 (11.2°C). The absolute maximum of 21.2°C on the 15th is 24th warmest April day since 1900.

The mean maximum temperature was notably above average (14.4°C), the 4th highest on record behind 1914, 2007 and 2011.

Sunshine was well above average too; this was Durham’s 22nd sunniest April. Some of the coolest days were the least sunny, for reasons explained below. Both the 9th (10.7°C maximum) and the 13th (7.8°C maximum) had only 0.1 hour of sunshine.

For much of the month, anticyclonic conditions dominated and, depending exactly where the anticyclone sat, Durham either basked in unseasonable warmth or was chilled by winds coming off the cold North Sea, often with full cloud cover too. The lowest maximum was on the 13th (7.8°C), a day with a brisk wind from the ENE at an average speed of 11.2kph, a maximum gust of 41.8kph, and only 0.1 hour of sunshine. Contrast this with the warmest day of the month, the 15th: a maximum of 21.2°C, an average wind speed of 2.2kph, a maximum gust of 19.3kph and 10.5 hours of sunshine. Cyclonic weather was only influential at the very start and end of the month. On the 2nd, the passage of a cold front produced a gust of 78.9kph at 10:45 associated with a strong westerly wind.

Emeritus Professor Tim Burt
Department of Geography
Durham University