London’s September extremes since 1959

September in recent years has often been a more summery month than August. But this month in some years can see a rapid onset of autumn.

I’ve put together a few top 10s of stats for Wanstead, St James’s Park and Heathrow for the month of September.

september extremes

SJP september

heathrow sept

Some national UK September values according to TORRO

Hottest: 35.6C Bawtry, South Yorkshire – 2nd 1906
Coldest: -4.5C Dalwhinnie, Highland, – 26th 1942
Wettest: 190.7mm West Stourmouth, Kent – 20th 1973

In terms of climatology September maxima, considering the 1981-2010 average, shows a slight decrease through the month, though around the 1st and the 22nd there is often a spike. This would reflect the September singularities; early September warmth occurs in 82 per cent of years while the ‘Old Wives Summer’ has a 64 per cent probability.

september mean

 

The average rainfall graphic shows that downpour amounts are variable through the month. A tendency for dry weather to the 8th prevails before the trend increases, the wettest days usually 13th and 19th.

sept rain

 

 

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