A severe cold snap overnight prompted the Met Office to release a yellow snow and ice warning for most of England and all of Wales, as well as large parts of Scotland.
Drivers have been told to be wary for patches of ice, and journeys are expected to take longer after temperatures plummeted.
Official advice said: "Icy stretches are likely to form perhaps leading to some disruption to travel with snow falling for some places.
See the Met Office's latest forecast here:
"What to expect: some injuries from slips and falls on icy surfaces; probably some icy patches on some untreated roads, pavements and cycle paths; some roads and railways likely to be affected with longer journey times by road, bus and train services.
"The warning has been updated to make this a dual snow/ice warning with the area extended southwards across more of central and southwest England. The warning end time has also been delayed until the end of Friday."
An ice warning is also in place throughout Northern Ireland.
Alex Deakin from the Met Office said that the weather in England and Wales could get even colder over the next few days.
He said a mixture of sleet and snow would "creep across" England and that snow might be seen in low-lying parts of the Midlands and Wales tomorrow morning.