The UK has enjoyed its hottest day of the year so far.
Temperatures at Heathrow Airport in west London reached a sweltering 28.6C today.
The south east of England enjoyed the hottest start to the week, with the mercury only reaching the high teens in Northern Ireland and Scotland.
The UK's previous high of 2021 was 28.3C in Northolt, north-west London, on June 2.
The Met Office has warned people to be prepared when heading out and about due to high UV and pollen levels across much of England and Wales.
The hot start to June is due to make way for more changeable conditions mid-week as thunderstorms threaten disruption.
A yellow weather warning is in place for the eastern half of Wales and much of England from Wednesday to Friday and the Met Office said there is potential for travel disruption and flooding.
Meteorologist Dan Stroud said: "We're likely to become increasingly changeable towards the weekend.
"There is still the potential for some more settled spells and some warm weather is possible later in the month, but it is generally turning more changeable from this weekend."
Away from the sizzling south east, Euro 2020 supporters cheering on Scotland north of the border had much cooler conditions.
While there was a high of 17C in Aberdeen, the temperature was a few degrees cooler still in Glasgow.
The city, where Scotland kicked off their Euro 2020 campaign against the Czech Republic at Hampden Park, reached only about 14C, the Met Office said.
Northern Ireland saw a high of 17C on Monday while Wales enjoyed a balmy 24.4C.
A day earlier, Northern Ireland and Wales recorded their warmest day of the year so far, with 27.4C in Cardiff and 25.3C at the Giant's Causeway in Co Antrim on Sunday.
