More snow could be on the way with rare weather meaning winter could be extended.
Met Office forecasters say an atmospheric event is taking place known as a Sudden Stratospheric Warming, which could mean it will stay cold in the weeks ahead.
It causes temperatures in the stratosphere – the layer of atmosphere reaching more than 30 miles above the Earth’s surface – to rise to 50C.
Similar events have previously brought cold weather to the UK linked to a weakening of the polar jet stream bringing weather across the Atlantic.
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Martin Lewis, deputy chief operational meteorologist at the Met Office, said: “A Sudden Stratospheric Warming even is now expected to occur and will peak over the coming weeks.
”The resulting impact on the weather in the UK is still hugely uncertain, but there are some signs of conditions that an easterly flow could develop across Europe.“
He added: ”Although we wouldn’t expect continuously cold conditions, there is a greater chance of cold conditions recurring.“
Jet streams high in the atmosphere bring relatively mild air from the Atlantic, but when a Sudden Stratospheric Warming occurs, it can drag cold air from the east.
The Met Office says they ”don’t always result in this outcome, but a cold snap follows more often than not“, so the event greatly increases the risk of wintry weather.
Forecasters can predict these events a week in advance and can detect them using satellites.
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The last one was four years ago. Schools were closed in Scotland today and families in parts of England faced a snowy start to the half-term holidays today as an Arctic blast hit the UK.
Temperatures plunged to below zero on Sunday night and snow covered large swathes of the country this morning amid warnings that ice could form on untreated roads and cause slips and falls.
Parts of Scotland saw temperatures plummet to -6C, with more wintry shows expected. In Wales, two walkers were rescued on Sunday after becoming stuck in snow and ice at 985ft on Snowdon.
The Met Office has issued a yellow warning of snow and ice across large swathes of the UK today with weather warnings in place until mid-morning for much of Scotland.
The forecast says: Some roads and railways are likely to be affected by snow with longer journey times by road, bus and train services. Some flooding on roads is also possible.”