Some parts of Scotland, particularly the North East, have already seen wintry weather over the past few days while overnight temperatures in Northern Ireland last night fell to -8C, making it one of the coldest nights in April on record.
And the Met Office has warned that colder temperatures will continue into May, with the chances of a sunny May bank holiday vastly reduced.
Met Office spokeswoman Nicola Maxey said: “The weather has started to change and it is coming from the Arctic.
“We have had a long stretch of quite settled weather where high pressure has dominated, but that has moved out. This cold air has moved in from the Arctic and that is moving slowly south.”
Drivers have been warned to prepare for potentially treacherous conditions, with Scotland and Northern Ireland set to bear the brunt of the Arctic blast before it sweeps across northern England, Wales and the east coast.
Gale-force winds of up to 50mph are predicted to batter Northern Ireland.
Britain experienced its hottest day of the year so far less than two week ago, with Kent reaching 25.1C.
But temperatures have since nosedived and will struggle to make double digits in Scotland - colder than projected temperatures in Moscow.
Ms Maxey added: “We are in colder air for this week which is coming down from the Arctic.
“It looks like we are staying fairly unsettled into the start of May with temperatures average or a bit below average.”
Simon Williams, a spokesman for the RAC, said: “It’s very easy at this time of year for motorists to feel that wintry conditions have gone for good, but you can be easily caught out by some very changeable conditions.
“Our advice is to simply plan ahead and prepare for adverse conditions with the temperature set to drop this week, leading to more wintry conditions in some parts.
“It’s important to check essentials such as coolant and anti-freeze levels and give yourself time to ensure the engine starts, especially if the car has not been used for a few days as a cold snap can badly affect the battery.
“With the possibility of ice on the roads in parts of the UK, it is also important to leave more time for journeys and drive to the conditions to avoid the possibility of an accident.”