There was a brief warm spell around 9 September, on which date the highest September temperature for six years was recorded, but much of the rest of the month was cool. In fact it was the coolest September since 1993, and heavy rain during the third week caused floods. This was the result of a deep and slow-moving low pressure system delivering copious rain between 23 and 25 September. Prior to that it was dry in East Anglia and south-east England.
The mean maximum temperature in September ranged from 20.2C at St James's Park, London, to 12C at Lerwick, Shetland. The Central England Temperature (CET) was 13.1C, which is 1 degree below average. Daytime temperatures were between 0.2 degrees above average in East Anglia and 1.3 degrees below in western Scotland. The highest recorded temperature was 29.3C at both Writtle in Essex and Cambridge on the afternoon of 9 September. The coldest night was that of 22/23 September, when Braemar, Aberdeenshire, recorded a minimum temperature of -4.1C.
Across England and Wales there was 78mm of rain, which is 102% of the average. Scotland had 81mm, exactly on the average, while Northern Ireland had 98mm, or 123% of average. Much of that rain came from the slow-moving storm during the last week of September. Up to 22 September it was relatively dry, but the following three days had widespread heavy rainfall which led to significant floods. During that period 131mm of rain fell on Ravensworth, North Yorkshire. The wettest location through the month was Cluanie Inn, Wester Ross, which measured 325mm of rain, while Otterbourne in Hampshire was the driest with 24mm.
England and Wales had an average 171 hours of sunshine, which is 116% of the mean. Only 11 Septembers have been sunnier in the last 100 years. Scotland had 127 hours, or 111% of its average, and Northern Ireland recorded 139 hours, which is 113% of the average. Manston in Kent was the sunniest location with 196 hours of sunshine, while Kinlochewe, Wester Ross, had the lowest sunshine total with only 62 hours.