September 2013 was a fickle month that required more than one change of wardrobe as the winds blew hot then cold... and then warm again. However, whilst the changing winds brought yo-yo temperatures, they didn't often bring significant rainfall to the Anglia region; most of the rain fell during one unsettled week. High pressure both at the beginning and at the end of the month tended to keep other Autumn storms away.
Provisional statistics give 41mm of rainfall for the Anglia region, which is 75% of the 1981 to 2010 average. Sunshine amounts were precisely average with a total of 145 hours - around 5 hours per day but temperatures were very slightly cooler than normal with a mean daytime high of 18.5°C and a mean daytime low of 9.8°C.
What these September averages fail to highlight are the ups and downs of a fascinating month of weather; the hot and sunny beginning, the cold and wet middle, and the calm and foggy end to the month. September may have been a benign period overall but it was not without its interesting weather.
There were no signs of Autumn during the first week of September as high pressure over the near continent and gentle southerly winds brought a short blast of heat. Temperatures peaked on the 6th with a high of 30.2°C at Writtle in Essex. The heat even produced a torrential shower during the evening around Norwich before it turned cooler and wetter everywhere on the 7th.
After the heat came the rain. In fact, there was so much rain that the second week of September was the wettest week of the year so far. It also turned much colder with northeasterly and then northwesterly winds replacing the southerlies of the previous week. Those chilly northwesterlies continued to blow throughout the third week of September and Santon Downham in Suffolk came perilously close to a frost with an overnight low of 1.0°C on the 15th.
The final wet day of the month was the 19th before high pressure returned across the British Isles. As we approached the Autumn equinox and the nights became longer, clear skies, high humidity and light winds encouraged extensive fog to develop during the mornings of the fourth week - often slow to clear and impacting the morning rush hour. During the closing days of the month, a cool easterly breeze dispersed the mist and fog and the September sunshine returned.