Britain is set for an end to the glorious spring weather, with temperatures expected to plunge and snow even expected in some areas of the UK, the Met Office said.
Althought the mercury is set to rise to highs of 18C in parts of England and Wales for the rest of this week, the weekend is likely to see cloud and patchy rain from the north, bringing colder conditions and wintry showers along the North Sea coasts.
Temperatures will only reach 11C in the south, with sunny spells on Saturday morning turning to cloud for most of the UK.
There could even be snow in higher areas, experts say.
A cold and #frosty start this morning across England and Wales, though with plenty of #sunshine the temperature will quickly rise
Cloudy across Scotland and Northern Ireland with some #rain pic.twitter.com/Ra18ERcsrT
— Met Office (@metoffice)
Looking ahead to next week, the Met Office said: "Towards the end of March it will be largely dry, however, eastern areas will likely see showers of hail and snow at times, which will accumulate on higher ground and could give some snow and ice to lower levels during the night. A northeasterly wind will keep it cold.
"High pressure conditions should dominate through the beginning of April, bringing plenty of dry, fine weather with bright or sunny spells across the UK, particularly in west.
"Winds will be predominantly light, with any breezier weather bringing a significant wind chill, indeed it looks likely to remain colder than average with further chance of snow.
"Unsettled conditions will tend to gradually become more established from the northwest later, bringing spells of wind and rain."
The change in weather is bad news for some workers who have been making the most of this week's soaring temperatures while working from home.
But Mr Johnson said people must stay at home except for shopping for basic necessities and medical needs, for exercise but only once a day, and to travel to work only if "absolutely necessary".
Gatherings in public of more than two people who do not live together have been banned, but parks will remain open for exercise, with police being handed the power to step in to disperse gatherings and enforce the new measures with fines.