Temperatures are expected to plummet to -7C (19.4F) in some parts of the UK overnight as Arctic winds bring an end to the good weather.
The drastic change comes after the Met Office said highs of 17.9C (64.2F) were recorded in Pershore, Worcestershire, on Easter Sunday.
However, parts of southern England will drop to just 2C (35.6F) on Monday morning.
Sub-zero temperatures can be expected in parts of northern England, while the mercury could drop to -7C in some areas of Scotland.
The dire forecast came as people flocked to parks and public spaces, including Liverpool’s Sefton Park and Stratford-upon-Avon, in Warwickshire, to enjoy the sunshine on Easter Sunday.
Met Office forecaster Sarah Kent said: “We will see this plunge of much colder conditions coming in.
“It’s Arctic maritime air, which does mean it’s coming from the Arctic.
“So it’s going to be cold for everybody, but also windy too.
“The wind chill is going to be significant.”
Snow warnings are in place for northern Scotland, with as much as 15cm falling in higher areas.
The Met Office’s yellow warnings are in place from 4pm on Sunday until 10am on Tuesday for Scotland, with winds of up to 70mph forecast.
Coastal areas of eastern England, parts of Wales and Northern Ireland could also see snow showers on Easter Monday.
Southern England can expect to see some sunshine and highs of 7C later in the day, but gusts of up to 30mph will make the temperature “feel like” -1C, Ms Kent said.
Parts of the UK saw the mercury reach nearly 24C (75.2F) on Wednesday, a balmy high unlikely to be repeated on Easter Sunday.
Meteorologist Ms Kent said: “Today is a lovely day for an Easter egg hunt in the back garden, whereas tomorrow if you were doing one you’d probably want to wear three jumpers.”