Brits are set to sizzle this week as a 'Saharan spurt' sends temperatures rocketing to 31C.
It looks set to be one last gasp of summer as a 48-hour September heatwave hits.
The Met Office says a 1,500 mile-wide hot spurt of scorching air originating from the Sahara desert will see the mercury reach 30 or above this close to autumn for the first time in four years.
The UK will enjoy sweltering highs not seen for weeks, despite the summer being all but over, while recent weeks have seen Britain battered by heavy rain and strong winds.
Met Office forecaster Greg Dewhurst said charts suggest 30-31C on Monday in the southeast, with similar on Tuesday in East Anglia.
"We're going to see a current of warm air coming out of Spain and France engulfing much of the country," said BBC meteorologist Tomasz Shafernaker.
Lots of sunshine will develop across England and Wales from Monday morning, with Scotland "drying out" after further rain.
The far north will only see around 20C but the further south the more intense the heat wave, with most likely to see temperatures well into the 20s.
"It looks like Tuesday is going to be every bit as warm across the southeast," continued Mr Shafernaker.
There could be highs of 27 or 28 again on Wednesday, but as we head towards the end of the week the heat will begin to move away and temperatures will drop to the low 20s in the warmest parts, Met Office's John Griffiths said.
The meteorologist added: "It's not that unusual for this time of year, we quite often get warm spells of weather in September."
But these temperatures will still be some way off the highest September temperature ever recorded, which was 35.6C on September 2, 1906.
The hot weather comes as rules on socialising are tightened across England in a bid to halt the growing numbers of coronavirus cases.
From Monday, it will be illegal to meet in groups of more than six people with the threat of fines for anyone found flouting the law.
Due to rain expected in Scotland today, the Scottish Environment Protection Agency has put seven flood alerts and three warnings in place.
UK 5 day weather forecast
Most parts dry with plenty of warm sunshine, becoming hot in the south. Cloudy across northwest Scotland with some light rain. A few showers possible across Northern Ireland later.
A dry and sultry night across central and southern areas. Cloudier in the north, with cloud increasing in the west later giving a risk of a few showers.
Cloudy with outbreaks of rain in far north. Very warm across central and southern areas, and hot in the southeast, though cloudier than Monday. Perhaps a few thundery showers later.
Outlook for Wednesday to Friday:
Some rain moving south across northern and central areas Wednesday into Thursday. Otherwise mostly dry and fine. Cooler than of late across the north and east, warm in the south.