Christmas Day is expected to be the hottest in years after Christmas Eve was recorded as the warmest since 1997, according to the Met Office.
The weather agency said parts of the UK are expected to hit 14C.
Most of the country will remain mild and cloudy with drizzle at times ruling out a white Christmas, apart from the mountains in northern Scotland which could see snow.
Temperatures are unlikely to exceed the warmest Christmas Day on record when the temperature reached 15.6C in 1920.
However, Met Office forecaster Dan Stroud said this Christmas could see the “warmest Christmas day since 2016” when the UK hit 15.1C.
On Sunday, the weather agency said temperatures reached 15.3C at Heathrow, west London.
The warmest Christmas Eve on record was in 1931, when 15.5C was recorded in Aberdeen and Banff in Scotland.
Met Office forecaster Liam Eslick said: “It’s been an exceptionally mild couple of days across all of the UK, temperatures have been well above average for the time of year, the maximum for December being 7C.
“Temperatures (on Sunday) reached 15C in quite a few locations across the UK, the highest being 15.3C in two locations – one in Heathrow and one in Cippenham, Berkshire.”
Christmas Eve as it happened
Mr Eslick said there could be breaks in the weather on Christmas Day if people are looking to “go out and about”.
He said that Boxing Day is probably going to be the best day if people are looking to go for a walk.
No more white Christmases?
With 15.3C recorded at Heathrow, it was certainly one of the warmest Christmas Eve’s in recent years – but the warmest on record was in 1931 when 15.5C was recorded in Aberdeen and Banff.
That was obviously some time ago, although that may have been down to mountain effects (the Fohn Effect, whereby air descending downwind of a mountain range is warmer than on the upwind side), rather than a more general warmth.
It is hard to draw any real conclusions, especially where records for a single day are involved.
But the relatively high temperatures are consistent with the general warming we’ve been experiencing (it looks like this is the first year the Central England Temperature has been above the 1961-1900 average in every month, for example), coupled with a south-westerly flow, thanks to the position of the jet stream.
Does it mean no more white Christmases?
No – firstly, it looks like there’ll be snow over the northern Scottish hills this Christmas, while more generally, changes in the jet stream may put us on the cold side in future years, bringing an increased risk of snow.
The UK is drawing in warmer air from the south, contributing to this unusually mild weather.
Two separate yellow wind warnings were issued by the Met Office in Scotland and northern and central areas of England for Christmas Eve, saying people should expect travel disruption, damage to buildings and power cuts, while the rest of the country may see showers.
In Wales persistent and heavy rain could cause disruption to transport and power supplies with the possibility of flooding.
And further yellow weather warnings have been issued by the Met Office for later in the week, including parts of Scotland which could face heavy rain and snow.