Temperatures across large parts of Britain are increasing and could peak at 27C this week, forecasters have said.
High pressure currently over Europe is set to drift northwards bringing warm southerly winds and sunshine to as far north as Scotland.
Helen Rossington, senior meteorologist at MeteoGroup, said temperatures would climb from Tuesday with a high of up to 24C in parts of south east England and Lincolnshire.
"At the moment, it looks like Friday, and possibly Saturday are going to be the warmest days of the week with temperatures probably getting locally up to 27C in the south east corner of England, Lincolnshire and probably East Anglia.
"I think on Sunday, the high pressure will start to move away to the west which is not so good, because that means that the winds start to come round again from a northerly direction.
"If you are in western Scotland it is not going to be so great, but because high pressure is the dominant feature, it is going to be a very warm and pleasant end to September."
She said temperatures had reached a high of 22.9C in Mildenhall, Suffolk, on Sunday. Although the forecast is good for Monday, she said there could be some heavy showers in parts of south east England.
The mini heatwave compares to an average maximum temperature for September of 19.1C in south east England.