Storm Conor is set to bring strong winds and snowfall as it sweeps in, bringing an end to an "exceptionally mild" Christmas Day.
The mercury rose to 15.1C in Dyce, Aberdeenshire, pushing the record of 15.6C (60F) registered in Devon in 1920.
The unseasonably warm weather will give way to snow and potentially blizzard conditions as gusts of up to 90mph hit on Boxing Day.
Festive travellers are being urged to check before setting off as the stormy weather is predicted to cause disruption.
After a lull following the fallout from Storm Barbara, warnings have been issued for high winds and snow.
The Met Office issued a yellow "be aware" wind alert for Christmas Day for the Highlands, Western Isles, Orkney and Shetland.
A gust of 85.5mph was recorded at Scalpay Bridge in the Outer Hebrides on Sunday while at Castlebay in Barra speeds reached 74.9mph, the Western Isles Council said.
Emma Salter from the Met Office said it had been an "exceptionally mild" Christmas, but warned of falling temperatures and difficult conditions on Boxing Day.
She said: " Up in Scotland we have seen some quite strong gusts today already, 60mph winds, and some large waves too.
"That wind is due to strengthen tonight, and coupled with the snow it could be quite a difficult day tomorrow for people trying to get out and about, particularly the ferries and transport networks.
"There is the potential for blizzard conditions temporarily as well in that strong wind and snow."
Christmas Day was mild across the UK, with a high of 15C in Hull and 14.7C in Exeter but t emperatures will fall to lows of 6C in parts of northern England, closer to the December average, the forecaster added.
Snow affected several routes in the north east of Scotland while restrictions were put in place on many bridges due to the windy conditions and the Dornoch Bridge was closed.
Alerts are also in place for the north west and north east of England, and Yorkshire and Humber where gusts of around 50-60mph are forecast.
On Boxing Day a more serious amber "be prepared" warning has been issued for Orkney, Shetland and the most northerly part of the Highlands where winds could push 90mph.
Those areas were worst hit by Storm Barbara, which cut electricity to more than 25,000 homes.
Elsewhere, gales could hit parts of Grampian and Strathclyde, while snow alerts have been issued for central Scotland northwards as Storm Conor drags Arctic air across the region as it passes to the north of the country.
Snow accumulations of 5cm to 10cm are expected above about 200 metres, and 10cm to 15cm above about 400 metres, with drivers warned to be aware of icy patches.
Flood alerts are in place covering Tayside, Caithness and Sutherland, Orkney, Scottish Borders, Shetland, Skye, Easter Ross and Great Glen and Lochaber and the Western Isles, while local flood warnings have been issued for Tayside and Caithness and Sutherland.
Scotland's Transport Minister Humza Yousaf chaired a meeting of the Scottish Government's resilience team on Sunday with representatives of the Met Office, Transport Scotland, Police Scotland and the Scottish Environment Protection Agency (Sepa).
He said: " Our responders in the north have scarcely had a chance to recover from these conditions but now Storm Conor is set to bring the next test during Boxing Day.
"Of course many people will be travelling to meet loved ones and spend time with their families at this time of year and we would remind the public to check before they travel and delay their journey if they have to. Safety must be paramount and should take priority."