The UK is to set to bask in unseasonable sunshine over the coming days, with temperatures expected to reach up to 29C in parts of the country.
Met Office forecasters say the south east will have the warmest weather, which will peak on Wednesday and Thursday.
Temperatures in south Wales and the south west are expected to reach the low-20s, while Norfolk and Lincolnshire are expected to get up to the mid-20s on Thursday.
In the Midlands and Yorkshire, mercury will rise to the low-to-mid-20s on Wednesday, but will begin to cool the following day.
Scotland will have its warmest weather on Tuesday, with temperatures in the high teens, after which they will begin to fall.
A spokesperson for the Met Office said: "We may see some hot weather in the south east on Thursday but conditions will become cooler in the south over the weekend. The north will be wetter during this week.
"The north will become warmer over the weekend [in a] north-south reversal."
No Indian summer
The Met Office said that while it will be unseasonably hot, it is not an 'Indian summer', as some reports have suggested, as it is too early in the year: "An Indian summer is defined as a warm, calm spell of weather occurring after the first frost in autumn, especially in October and November," it said.
September is due to be warmer than normal, forecasters have said. According to The Weather Outlook, the first half of the month will be "well above the season average", but wetter conditions will come in the second week of the month.
"The second half of the month looks like bringing a mixed bag of weather. Some warmer and drier interludes are likely, but also unsettled and windy spells of weather," it said, adding that at the start of October, temperatures will be above average before the wet and windy weather sets in.
The September sunshine follows the Met Office announcement that this summer was the warmest, driest and sunniest since 2006.
Figures show the UK had 588 hours of sunshine, which is about 117% of the UK average, for the three months starting 1 June. The hottest day on record was 1 August, when Heathrow reached 34.1C.