Enjoy the warm spell while it lasts as an Arctic plunge is moving in and could even bring snow to some areas in Britain this weekend, warn experts.
Weather forecasters are predicting temperatures 6C below normal, and wintry showers bringing sleet to many parts of the UK and snow to higher ground in Scotland.
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A Met Office spokeswoman told the Evening Standard that London Marathon runners could face "wet snow" on Sunday, but that it won't settle. If this happens, it will be the first time any kind of snow has been reported at the London Marathon in its 35-year history.
The spokeswoman said: "There's a little bit of a possibility that there could be what we call wintry showers.
"It could be hail like we had last week or wet snow which isn't unusual for April.
"Nothing will settle on the ground and nothing will impede the runners so they won't have to worry about avoiding any snowmen."
Sky News weather presenter Isobel Lang echoed the prediction, suggesting there could be 'wet snow' and chilly conditions.
"Snow hasn't been reported since the London marathon began in 1981 so if this happens it would be a first."
Leon Brown, meteorologist at the Weather Channel, also told Aol Travel: "Keep the winter woollies on hand because another Arctic outflow will head south at the end of this week and will continue through next week.
"The forecast indicates that temperatures will often be 4 to 6C below normal during the day. Normally in late April, we would expect 12 to 13C in the north and 16C in the south, but 12C may be the best we'll see in the south and the north will struggle to reach double figures.
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"There is not a great deal of precipitation, but there will be scattered showers, especially over the north and east. There will be wintry showers with hail and sleet mixed in, and some snow over higher ground in Scotland.
"The Arctic winds will keep the higher runs on the Scottish Ski slopes open through to May."
At least we managed to get the cobwebs off the BBQ before the cold returns.