The warmest day of the year was recorded on Sunday, with the mercury hitting a scorching 23C in north Wales.
The Met Office confirmed the record on its Twitter page on Sunday afternoon, but also revealed there had been "mixed fortunes" for the rest of the country.
Scotland and Northern Ireland saw rather overcast afternoons with patchy rain.
The majority of England and Wales, meanwhile, basked in glorious May sunshine, with temperatures exceeding 20C.
As we head into the new week, it promises to be another warm day on Monday.
The Met Office forecasted the highest temperatures at about 4pm for all of the UK.
It'll likely remain cloudy for Scotland, but the majority of the country will be bathing in sunny and warm weather, it said.
South Wales was forecast to have the warmest weather on Monday, according to Ventusky weather maps.
Regions between Swansea and Cardiff were projected to hit 23C by mid-afternoon.
Meanwhile, Bristol, Exeter and Plymouth could reach 22C by 3pm. The rest of the England and Wales will be looking at anywhere between 14C and 20C for the remainder of the day.
The Met Office also warned about a wet start to the day for some regions, however.
It tweeted: "Overnight rain will linger across eastern Scotland during Monday morning, with some low cloud also across eastern England.
"Elsewhere will start the day dry with spells of sunshine, although it maybe chilly first thing in places."
UK five-day weather forecast
This evening and tonight:
Tonight rain and drizzle will gradually ease across Scotland, Northern Ireland and northern England to leave a dry night for most. Turning chilly under clear skies in northwest Scotland, Wales and northern England. Patchy low cloud pushing into eastern England.
Monday:
Low cloud and fog will quickly clear through Monday morning. A few showery outbreaks affecting Scotland, northern England and Wales, otherwise, a fine and dry day with warm sunny spells.
Outlook for Tuesday to Thursday:
Remaining largely settled this week with further warm sunny spells. Cloudier in the northwest on Wednesday with patchy rain. Chilly overnight with some fog patches but these clearing by day.
