A plunging polar front tussling with balmy 18C winds from the Continent will drive an autumn deluge before the first blast of winter.
Two huge air masses, one from the north and one from the south, will lock horns in battle as Britain’s weather hurtles along a rollercoaster.
Heavy rain across western and northern regions will persist through the middle of this week before temperatures to the north plunge.
The Highlands and mountains of Scotland will see the first "proper snow" of the season as southern regions simmer in tropical winds.
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Jim Dale, meteorologist for British Weather Services, said: “Rain during the middle of the week has the potential for disruption, particularly where it will be heaviest in western and northwestern parts of the country.
“But as we go towards the weekend, we are looking at the first ‘winter’ plunge of the season, and a potentially very cold snap to come.
“There is a battle going on between cold air from the North Pole clashing with much milder air from the south, and this is going to drive the big change in weather.”
Parts of Britain could hit -10C next week, he warned, as the risk of snow sinks south.
Parts of Britain could hit -10C next week, he warned, as the risk of snow sinks south
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He added: “The south is going to feel mild for a little while, but it is the north of the country which will start to feel very cold as we go into the second half of November, and this week, over high ground, they could see the first proper snow of the season.”
Temperatures in the south will hover around 15C through much of the week, with overnight highs in the teens.
Southerly winds across the region could bring 18C highs as high pressure builds to the north driving in cold winds.
Met Office meteorologist Aidan McGivern said: “This is going to be a week of significant temperatures contrasts from the exceptionally mild south to the north where it is going to turn colder eventually.
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Two huge air masses, one from the north and one from the south, will lock horns
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“We start off mild across all parts with low pressure is coming at us from the southwest, and moist and mild airflow bringing weather fronts in from the Atlantic.
“The rain in the west is going to mount up.”
Thursday will bring a ‘significant wind change’ across northern Scotland, he said, while the south continues to simmer.
The clash of both weather fronts will keep driving heavy rain across norther, central and western England.
Showers in the north will start to fall as sleet, hail and snow by Thursday as cold and warm air meet.
McGivern said: “It looks likely on Friday that Scotland, Northern Ireland and northern England will be cold and crisp, but further south it will be 15C, 16C or possibly even higher with 17C or 18C in the south by Friday.
“As we go into the weekend, it looks most likely that high pressure to the north will elbow its way further south and lead to colder and brighter weather across most parts.
“But to the far south and southwest, it may well stay cloudy, damp, and much milder.”
Hints of a chill snap come as the Met Office reveals the lack of cold weather so far could see this autumn land as one of the mildest.
A spokesperson said: “The persistence of above-average temperatures suggests that autumn 2025 is shaping up to be milder than usual, with fewer frosty nights and a delayed onset of winter chill.
“The wet conditions in the west and north may have implications for river levels and localised flooding, while the drier south and east could see continued agricultural activity and outdoor events.”