September 2016

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

Mean daily maximum: 18.7
Difference from average: +2.0

Mean daily minimum: 11.0
Difference from average: +2.3

Mean air temperature: 14.9
Difference from average: +2.2

Absolute maximum: 26.8 (13th)

Absolute minimum: 6.2 (18th)

Mean grass minimum: 9.2

Absolute grass minimum: 3.6 (30th)

Mean concrete minimum: 10.6

Absolute concrete minimum: 5.4 (30th)

Number of ground frosts: 0

Number of air frosts: 0

Mean soil temperature at 30cm depth: 16.3

Mean soil temperature at 100cm depth: 15.5

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

Total for the month: 44.2
Difference from average: -11.4

Percentage of the average: 80%

Wettest day: 10.0 (3rd)

Number of rain days (>0.25mm): 10

Number of wet days (=> 1mm): 7

3-month total rainfall to 30th September: 149.2
Difference from average: -22.8

6-month rainfall total to 30th September: 321.5
Difference from average: -24.7

12-month rainfall total to 30th September: 818.7
Difference from average: +169.7

Humidity
(averages for 09:00 hours GMT)

Relative Humidity: 85%

Sunshine
(all averages 1961 – 1990)

Total for the month: 114.6 hours
Difference from average: -9.4

Percentage of the average: 93%

Mean daily sunshine: 3.8 hours
Difference from average: -0.3

Sunniest day: 9.0 hours (18th)

Number of days with no recorded sunshine: 1

Cumulative total sunshine since 1st January: 952.7 hours
Difference from average: -171.7

ISSN1350-483

Comments on September 2016
September was an exceptionally warm month, the 4th warmest September on record since 1850, beaten only in 1865, 1949 and 2006 (which holds the record – 16.0°C). The mean maximum temperature was the 12th highest on record and the mean minimum temperature was the 3rd highest (beaten only by 2006 and 1949). The maximum temperature exceeded 20 °C on seven days, whilst the mean minimum was above 10°C on a remarkable 19 days (26 in 2006!). The maximum on the 13th was the 12th-equal warmest September day since 1850, the warmest September day since 1959; 1st September 1906 holds the record – 30.0°C! Both rainfall and sunshine were slightly below average.

Professor Tim Burt
Department of Geography
Durham University