Temperatures are set to plunge by as much as 10 degrees in less than a week, meteorologists said.
Britain's usual Indian Summer is expected to arrive tomorrow with temperatures climbing to a maximum of 20C (68F) in London.
But it will only last a day as northern winds bring a chill to the United Kingdom which has so far seen mild autumn temperatures.
The sunshine and warmth will give way to more unsettled weather with temperatures dropping by a few degrees every day to 8/9C (46.4F) on Friday.
Alexi Boothman, a forecaster with Meteogroup, the weather division of the Press Association, said: "Clearly, it is a gradual decrease in temperatures from the beginning of the week and it is quite a marked fall in the space of a week with the air mass being turned around."
