The weekend's hot weather, which saw crowds of people flock to beaches and beauty spots across the UK ahead of lockdown restrictions being eased in England, will come to an end this week, forecasters have said.
As people enjoyed temperatures of up to 28C (82.4F), emergency services attended incidents involving water, fires and littering, despite warnings being issued to the public.
And the hot conditions will remain until the middle of the week, when the weather will become more unsettled.
The Met Office says the west of England could enjoy highs of around 27C (80.6F) on Monday, while the South could see the hottest temperatures of the year so far on Tuesday, at up to 29C (84.2F).
But more changeable weather is expected later in the week, just days after the relaxation of lockdown measures in England, allowing socially distanced groups of up to six people to meet outside from Monday.
Meteorologist Marco Petagna said: "The sunny weather will certainly continue for a couple more days.
"But from Tuesday, we are starting to see some more unsettled weather across Scotland and the gradual trend will be turning cooler across the UK from Wednesday onwards."
He said northerly winds will bring cooler air and some areas in the south of England could experience thundery showers.
There could be showers or longer spells of rain on Thursday and Friday, and it will feel much cooler than of late.
The warm end to the month confirmed a significant milestone for the UK, with the nation recording its sunniest spring since records began in 1929.
The Met Office said there was more than 573 hours of sunshine between 1 March and 27 May, beating the previous record of 555.3 hours - which was set in 1948.
Figures published on Monday are also expected to confirm last month was the driest May for 124 years.
Over the weekend, people across the UK took advantage of the hot weather, visiting beaches and beauty spots, despite some authorities urging the public to stay away.
Brighton and Hove City Council asked people not to visit the area on Sunday and called on the government for more powers to implement a local lockdown.
A day earlier, crowds had to be evacuated from the beach and surrounding cliffs at Durdle Door in Dorset, when three people were injured after jumping from a 200ft (60m) sea arch.
And scores of people defied attempts to close the beach on Sunday, with people being encouraged by crowds to jump from the same place,
In Lancashire, one man died and two others were rescued and taken to hospital for treatment after a boat sank about a mile off the coast at Fleetwood on Sunday morning.
Authorities across the country urged people to stay away from open water, avoid lighting barbecues and to take litter home, as they reported having to fight fires and clear up rubbish left behind by visitors.
More than 100 firefighters in the North West battled to contain separate blazes as a result of the hot weather, with one moorland fire, covering 3 miles (5km) of land in Darwen, thought to have been started by a disposable barbecue.
In a tweet by North York Moors National Park on Sunday, it said: "There are no poo pixies or litter fairies here.
"Our rangers spent this morning at a beauty spot collecting 20 bags of rubbish, including nappies, socks, shoes, towels, chairs, gas canisters, BBQs, beer bottles, food and broken glass.
"Please do your bit and take your litter home."
Rochdale Council also tweeted, saying that local beauty spots had "taken a hammering" from visitors, and West Midlands Fire Service reported that firefighters spent the morning clearing up litter at Cannon Hill Park in Birmingham.