July 2021
SUMMARY OF THE METEOROLOGICAL READINGS AT DURHAM UNIVERSITY OBSERVATORY
July 2021
Temperatures (all temperatures in degrees Celsuis; all averages 1991-2020)
Mean daily maximum: 21.6 Difference from average: +1.4
Mean daily minimum: 12.8 Difference from average: +1.5
Mean air temperature: 17.2 Difference from average: +1.4
Absolute maximum: 28.5 (17th)
Absolute minimum: 8.5 (1st)
Mean grass minimum: 11.3 Difference from average: +1.8
Absolute grass minimum: 5.7 (1st)
Mean concrete minimum: 13.8
Absolute concrete minimum: 9.5 (1st)
Number of ground frosts: 0
Number of air frosts: 0
Mean soil temperature at 300 mm depth:
Mean soil temperature at 1000 mm depth:
Rainfall (all totals in millimetres; all averages 1981-2010)
Total for the month: 69.0 Difference from average: +7.0
Percentage of the average: 111%
Wettest day: 22.8 (4th)
Number of rain days (>0.1 mm): 14 Difference from average: -1
Number of wet days (=>1.0 mm): 10
3-month total rainfall to 31st July 2021: 184.6 Difference from average: +12.6
6-month total rainfall to 31st July 2021: 302.8 Difference from average: -43.4
12-month total rainfall to 31st July 2021: 844.4 Difference from average: +195.4
Sunshine (all totals in hours; all averages 1981-2010)
Total for the month: 177.7 Difference from average: +2.5
Percentage of the average: 101%
Mean daily sunshine: 5.9 Difference from average: +0.3
Sunniest day: 9.9 (17th)
Number of days with no recorded sunshine: 2
Cumulative sunshine since 1st January: 1008.9 Difference from average: +60.5
Note that the monthly sunshine total is now calculated from the UKMO E&NE regional total. Daily sunshine totals quoted here and in the data summary are uncorrected.
Wind (kph; all data from the West Building roof, Lower Mountjoy campus)
Average wind speed:
Maximum gust: ()
Comments on July 2021
July was a warm month, mainly because night-time temperatures were unusually high; daytime temperatures were less extreme but still very good in comparison to many previous Julys. The mean maximum is the 14th equal highest on record since 1843, whereas the mean minimum is the 4th equal highest; mean air temperature is the 6th equal highest on record. There were four days with maxima above 25 °C, two more than average but not an exceptional total. The absolute maximum of 28.5 °C is the 27th hottest July day in Durham since 1843. There were 21 days with maxima above 20 °C, five more than average, but again not an exceptional total. The absolute minimum for this July has only been exceeded four times; if we exclude 1846, 1853 and 1855 when the thermometer was unscreened, then only the record holder 1983 has seen a higher July absolute minimum (9.3 °C). The mean grass minimum is the 4th highest since 1874 (with 1945 and 2018), beaten only by 1926 (11.5 °C) and by 2005 and 2019 (both 11.6 °C). As expected there were no ground frosts; the last July ground frost in Durham was in 1940.
Rainfall was a little above average, the 106th highest July total in 172 years; this was so even with no rain at all recorded between the 13th and 26th inclusive. Sunshine too was very close to average.
Emeritus Professor Tim Burt
Department of Geography
Durham University