Forecasts predict that the & # 39; mild air & # 39; will move on weekends to see the 17C peak.
Martin Bowles, an operational meteorologist at Met Office, said: "It is very mild at temperatures slightly above average this week.
"We expect Friday's temperature to be 17C in some parts of Scotland and Wales, which is an average of 6 degrees this year."
But next week, the cold air of Eastern Europe will move inland, and the snowy weather will lead to dramatic changes in the weather system.
"Temperatures will be below average, and snow will fall on top of the mountain in northern Scotland.
"There will be quite a lot of frost in the country.
"We are going to start receiving east winds in Poland and Russia. The official temperature is 7C, but it feels like 2C or 3C but it will be very cold."
As the UK's low-pressure system moves, it will "feel more like Moscow".
John Hammond, chief meteorologist at Weathertrending, said, "The fresh wind this week will be replaced by a chilly neighborhood early next.
Piers Corbyn, WeatherAction's forecaster, added: "The aggressive low-pressure system will change from the northwest to the colder conditions next week.
"We expect heavy snowfall and very cold winds in the Northern Hemisphere will cause early winter weather and even the risk of rainy weather throughout Southern England.
"This pattern will last until December and December, where there is a risk of a snowstorm in a broad blizzard in Scotland and the north."