The Met Office has warned there is colder weather to come after snow and sleet showers hit the UK on Tuesday.
Wednesday is expected to be the chilliest day of the week, with northern areas waking up to temperatures of minus 2C (28F).
Coastal areas can expect more snow and sleet showers throughout the day.
The Met Office issued a yellow severe weather warning until 11am for ice across much of the country.
The alert says ice is likely to form on Wednesday morning, warning of the risk of falls on icy surfaces and ice on roads, pavements and cycle paths.
A spokeswoman said Northern Ireland saw “some significant accumulations” on Tuesday which later “pushed across Wales, central parts of England and towards the South East”.
“We’ve seen a few centimetres in particular over the hills, but also a good dusting of snow to lower levels as well.”
She said Wednesday will be one of the coldest days of the week, “but with a lot of sunshine to compensate“.
“Those concerned about the yellow warnings should allow extra time for journeys and take extra care on untreated roads and pavements.
“It’s patches of ice left over from snow showers that people should look out for.”
The weather caused some disruption to rush-hour rail services.
Greater Anglia Rail advised customers that trains will be running with speed restrictions between Hackney Downs and Cambridge and services may be cancelled, delayed by up to 15 minutes or revised.
Merseyrail said that due to ice preventing electricity from reaching the trains, services between between Aintree and Ormskirk, Hooton and Ellesmere Port, and Hooton and Chester have been cancelled.
Whilst other Merseyrail lines are running, passengers have been warned to expect severe delays and cancellations.
Some coastal showers will continue overnight on Wednesday while many central and eastern areas are expected to be clear, cold and frosty.
Although the weather will warm slightly towards the end of the week, more cold weather is set for the weekend.
The spokeswoman said: “Gradually some slightly warmer air will push in for the latter part of the week, but we have a band of rain pushing in Saturday which will push much colder air in behind it.”
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