May 2025
SUMMARY OF THE METEOROLOGICAL READINGS AT DURHAM UNIVERSITY OBSERVATORY
May 2025
Temperatures (all temperatures in degrees Celsius; all averages 1991-2020)
Mean daily maximum: 17.5 Difference from average: +2.1
Mean daily minimum: 7.1 Difference from average: +0.6
Mean air temperature: 12.33 Difference from average: +1.3
Absolute maximum: 25.6 (1st)
Absolute minimum: (-0.6, 6th)
Mean grass minimum: 4.9 Difference from average: +0.3
Absolute grass minimum: -2.7 (6th)
Mean concrete minimum: 8.4
Absolute concrete minimum: 0.9 (6th)
Number of ground frosts: 3 Difference from average: -1
Number of air frosts: 1 Difference from average: 0
Mean soil temperature at 300 mm depth: 15.0
Mean soil temperature at 1000 mm depth: 12.7
Rainfall (all totals in millimetres; all averages 1991-2020)
Total for the month: 23.2 Difference from average: -21.3
Percentage of the average: 52%
Wettest day: 8.8 (23rd)
Number of rain days (>0.1 mm): 8 Difference from average: -6
Number of wet days (=>1.0 mm): 6
3-month total rainfall to 31st May 2025: 48.2 Difference from average: -91.5
6-month total rainfall to 31st May 2025: 194.4 Difference from average: -144.9
12-month total rainfall to 31st May 2025: 498.8 Difference from average: -182.2
Sunshine (all totals in hours; all averages 1991-2020)
Total for the month: 244.4 Difference from average: +57.4
Percentage of the average: 131%
Mean daily sunshine: 8.1 Difference from average: +2.1
Sunniest day: 13.1 (11th) Number of days with no recorded sunshine: 0
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: 2.02
Maximum gust: 19.7 (25th: 12:15, WNW)
Pressure (mbar)
Average: 1017.8
Maximum: 1029.9 (15th, 23:00-23:30; 16th, 00:15) Minimum: 996.2 (25th, 04:15, 04:30)
Comments on May 2025 and Spring 2025
This was the 8th warmest May on record (12.33 °C, 1.3 °C above average), marginally warmer than May 2023 but a little cooler than May 2022 and the warmest May on record, 2024 (13.59 °C). Thus, the 2020s have experienced some remarkably warm late-spring weather. Of the ten warmest Mays on record at Durham, five have been in the 2020s! The warmest day was the 1st (25.6 °C), the warmest May Day on record and the 9th warmest of any days in May. Unlike last year when May was wet, this May was quite dry, the 28th driest on record. Only ten Mays have had fewer rain days since 1850; there were just three in 1859, the driest May on record. There was an absolute drought (15 days or more with no rainfall) from the 6th to the 21st inclusive (16 days). This was the 7th sunniest May on record, the sunniest since 2020. There was some measurable sunshine every day.
We have had the 3rd warmest spring on record (9.80 °C); only 2004 (9.86 °C) and 2017 (9.85 °C) have had warmer springs. This was also the 3rd driest spring on record (48.2 mm); only the springs of 2020 (42.4 mm) and 1956 (45.3 mm) have been drier. The 2025 spring saw just 35% of the normal rainfall, 88.8 mm less than expected. This counts as a drought, where a drought is defined as a period of 3 months with at least a 50% rainfall deficit; in this case the deficit was 65%. There were just 26 rain days this spring, the equal 4th lowest total on record, 18 fewer rain days than in a normal spring. It was by some margin the sunniest spring on record (since 1882); the May 2025 total (650.5 hours; more than 50% of the possible total) easily surpassed the previous record holder (2020: 630.3 hours). The results suggest that one manifestation of climate change at Durham is a tendency for warmer, drier, sunnier springs with May more like a traditional summer than spring.
Emeritus Professor Tim Burt
Department of Geography
Durham University