Summer might be over but the first week of autumn is set to be warmer than average with temperatures hitting as high as 25C.
As many children return to school this week, it is set to get warmer "day on day" from Tuesday onwards, a meteorologist at the Met Office said.
Krista Mitchell said by Friday temperatures could be as high as 24C or 25C during sunny spells in the south - with the overall average temperature for September being a significantly lower 16C or 17C.
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As the new season gets underway, cloud and rain will push in from the north tonight, pushing southwards, making the first morning of autumn quite cloudy and dull with outbreaks of rain.
Through tomorrow, dry and brighter conditions will push in from the north west, and while south-eastern parts will stay cloudy for much of the day with outbreaks of rain, those conditions are expected to clear - and then temperatures are set to increase.
Krista Mitchell, meteorologist at the Met Office, said: "What we've got is high pressure building which is bringing more settled conditions, and also slightly warmer conditions as well.
"We had a pretty cool August, temperatures in places below average for the last couple of weeks, so it looks like it's warming up as we go into the middle of the week.
"It's not going to be wall-to-wall sunshine but where there are sunny spells it's going to feel pretty warm.
"Generally temperatures are rising day on day from Tuesday, basically. By Thursday or Friday, we could see 24C or 25C in the sunny spells in the south."
She added: "It's not a negative picture for the north by any stretch."
Scotland and the north of England could see temperatures of 20C or 21C.