The UK will wake up to sub-zero temperatures as wintry conditions grip the country.
Temperatures could plunge to below -10C (14F) with forecasters warning of snow and ice.
Before 10pm on Thursday night, the mercury had already fallen to below -4.7C (23.5F) in Braemar, Scotland, dropping about a degree or so every hour.
It will be a #frosty start for many, with some #icy patches in eastern parts for the morning commute. Meanwhile, rain and hill #snow will arrive into some western parts #weatherawarepic.twitter.com/xio6r56hjy
— Met Office (@metoffice) January 17, 2019
Met Office meteorologist Alex Burkill said: "Winter's here now properly. It feels like winter and the weather's resembling it."
He said cloud rolling in could be enough to stop more extreme plunges overnight, but added that lows of -10C and -12C (10.4F) are still possible.
"I think there is still a chance that we could get below -10C," he said.
Mr Burkill said the coldest time will be around 6am or 7am, and the chilliest place is likely to be sheltered parts of Scotland such as Braemar.
"Generally, across much of England, it's going to be very cold and frosty," he said.
Shap in Cumbria could see a low of -8C (17.6F), Mr Burkill said.
In order for Thursday night to be the coldest of the winter so far, it has to beat the low of -10.5C (13.1F) recorded on January 3 in Braemar.
The Met Office has issued a yellow warning for snow in Wales from 8am until 1pm, when 2-4cm of snow is expected.
"I think in Wales, many places are likely to see some sleet or snow," Mr Burkill said.
A snow and ice warning is in place along the east coast of England until 10am on Friday morning.