September 2024
SUMMARY OF THE METEOROLOGICAL READINGS AT DURHAM UNIVERSITY OBSERVATORY
September 2024
Temperatures (all temperatures in degrees Celsius; all averages 1991-2020)
Mean daily maximum: 16.2 Difference from average: -1.1
Mean daily minimum: 9.4 Difference from average: +0.2
Mean air temperature: 12.8 Difference from average: -0.5
Absolute maximum: 21.8 (17th)
Absolute minimum: 1.3 (13th)
Mean grass minimum: 8.1 Difference from average: +1.0
Absolute grass minimum: -1.3 (13th)
Mean concrete minimum: 10.0
Absolute concrete minimum: 2.3 (13th)
Number of ground frosts: 2 Difference from average: +1
Number of air frosts: 0 Difference from average: 0
Mean soil temperature at 300 mm depth: 15.6
Mean soil temperature at 1000 mm depth: 15.2
Rainfall (all totals in millimetres; all averages 1991-2020)
Total for the month: 97.8 Difference from average: +41.0
Percentage of the average: 172
Wettest day: 23.0 (25th)
Number of rain days (>0.1 mm): 16 Difference from average: +1
Number of wet days (=>1.0 mm): 9
3-month total rainfall to 30th September 2024: 188.2 Difference from average: +3.2
6-month total rainfall to 30th September 2024: 366.8 Difference from average: +25.0
12-month total rainfall to 30th September 2024: 885.8 Difference from average: +204.8
Sunshine (all totals in hours; all averages 1991-2020)
Total for the month: 120.0 Difference from average: -13.2
Percentage of the average: 91%
Mean daily sunshine: 4.0 Difference from average: -0.4
Sunniest day: 9.5 (17th)
Number of days with no recorded sunshine: 6
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: 5.9
Maximum gust: 70.8 (10th, 11:30, N)
Comments on September 2024
September was only the second month with below-average temperature so far this year. Even so, it ranks equal 73rd highest since 1843 (n=182) so in the third quartile. It was the coldest September since 2015, but there were no days with a maximum below 10 °C. The mean minimum was the 38th highest whereas the mean maximum was only the 108th highest, showing it was daytime temperatures that proved disappointing. The relative warmth of nights is confirmed by the mean grass minimum temperature being the equal 13th highest on record.
This was the 24th wettest September on record since 1850, although only half the record September rainfall (1976, 193.2 mm). Since 2015 five Septembers have had similar amounts of rainfall whereas the other five have had only about half the amount, showing September to be rather variable in this regard. Sunshine was just below average.
The atmospheric circulation was notable in that there was a predominantly ‘north-eastern’ air flow. At 0900, 15 days indicated a wind direction between North and East, plus four from the north-west and one from east-south-east.
Emeritus Professor Tim Burt
Department of Geography
Durham University