An historical perspective of the climate statistics for Coventry during September 2020

Temperature

In the first decade of the 21st century, the average monthly September temperature was 14.9°C, indicative of recent warming, compared to the warmest decade of the 20th Century, in the 1980s at 14.2C.

However, in the first nine years of this decade (2011-2019), September has averaged 14.5C, even though September 2016 was the fifth warmest September in the Central England Temperature Series since 1659.

So this year’s September mean monthly temperature of 14.5C (0.1C above normal) is about what we might expect since the Millennium, though slightly warmer than September 2018 (14.3C) and 2017 (13.9C), but cooler than last year (14.6C).

Just out of interest, we haven’t had a September air frost in Coventry since 1974, and only for since 1892 (1919, 1943, 1944 and 1974).

• 15th the hottest day of the month recorded a maximum temperature of 28.8C; this was the warmest September day in Coventry since 1949 (28.9C)..

• 28th the grass minimum temperature fell to -2.8C; this was the lowest such value in September since before 1978.


Rainfall

During the first 19 years of the 21st century, September rainfall averaged 49.0mm, compared to 76.1mm in the decade 1991-2000, suggesting a considerable drying trend in this first autumn month of the season in Coventry.

With 21.8mm of rainfall in September 2020, this has been the driest September in Coventry since 2014 (4.8mm), with 38% of the monthly total falling on the last day of the month.

Only four September months have been drier than 2020 in the past 49 years (1989 1996 2009 2014).

Sunshine

Thanks to the Clean Air Acts of the last century, September sunshine totals in Coventry had increased by 20% during the 20th century, with an average of 128.3hr per month from 1901 to 2000.

This trend has continued since the Millennium in Coventry, with a further 9% increase from 2001 to 2019 (139.5hr)

With 174.5 hours of sunshine, 27% higher than normal, this has been the sunniest September in Coventry since 2003 (174.9hr).

Only six September months have recorded more sunshine than this year since 1914 (1929 1959 1964 1986 1991 and 2003).

It is interesting to note that September 2020 recorded more sunshine in Coventry than both July and August; this is the first time this has occurred since 1966, though it also happened in 1954 1942 1915 1914 and 1895.