BRITS are braced for chilly temperatures after the Met Office warned that Arctic air will sweep through the country.
Forecasters say the UK is expected to see "considerably colder" conditions over the next few days.
The wintry conditions will bring below average temperatures and a chance of snow on the highest peaks in Scotland.
Freezing winds swept southwards through the country overnight with "all of the UK" experiencing "colder arctic air", say forecasters.
Met Office spokesman Jonathan Vautrey said temperatures for most of the week will be 4-6C below average.
Patchy rural frost will develop by Thursday night with overnight temperatures tumbling.
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And forecasters say Friday is likely to be the coldest morning.
He said: “Many of us will see temperatures in the mid-teens – around 13 to 14C – whereas normally at this time of year it would be at least 16 to 18C, if not closer towards 19 to 20C in the far South East, places like London.
But temperatures will feel even colder and "more like single figures" for a lot of places due to strong winds.
The forecaster said Thursday into Friday is likely to be the coldest night of the week, as temperatures in rural areas could drop below freezing.
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Mr Vautrey added: “We could see some patchy frost developing in rural areas across all nations of the UK, particularly Scotland.
“For people waking up on Friday morning it could be quite a shock to the system as they’re walking out of the door.”
The highest peaks in Scotland may see some snowfall as a result of the frosty temperatures.
“There is a small chance of some snow falling over the highest mountains of Scotland, but you’ll have to hike quite a way before you see any snow,” Mr Vautrey said.
Earlier in the week on Wednesday, wet, windy and cold weather will prevail as the cold front moves in, with scattered and blustery showers widespread in the North and West.
Showers will continue into Thursday but will be accompanied by some sunshine in many areas.
The weather will become a little drier and less windy throughout the day - before the UK sees its coldest night going into Friday.
Despite the frosty temperatures, Friday will be largely dry across the UK, until a front of rain strikes the North West later in the evening.
However, the Met Office said the cold spell is not expected to last too long and temperatures will start to climb back up towards average by the weekend.
Friday will be the end of the cold snap as temperatures begin to climb back up by the weekend, as warmer air “pushes back” against the cool Arctic winds, the Met Office said.
It comes after days of heavy rain, thunder and lightning, with many in the capital posting photos and video of the flashing purple skies upon the skyline.
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Previously, Met Office forecaster Craig Snell said on Sunday: “As we go through into Tuesday and Wednesday and beyond, we will start to see even cooler air begin to move in from the Arctic.
“Our first autumn chill of the season is coming our way into the middle part of the week. It will bring temperatures around the mid-teens by day and by night, some of us will be falling into the low and mid single figures.”
UK long range weather forecast
The Met Office forecast from September 15 to September 24
Initially fine for most locations during this period the early part of this period, with a weak front bringing cloud and patchy rain across central parts of UK returning northwards through Sunday into Monday.
Perhaps bringing rainfall to the northwest, which could be heavy for a time across the hills of Northwest Scotland.
This pattern is then likely to persist, with many areas likely remaining mostly fine, and the greatest chance of cloud and rain being across the far west and more especially northwest.
Temperatures during this period are likely to be on the warmer side of average, but with settled conditions warm days could be offset by a few chilly nights.
Towards the end of this period there is a signal that the more settled conditions may cease.