All four nations of the UK have seen temperatures hit 30C for the first time in five years, as Britain swelters in another hottest day of the year.
Highs of 30C and over were recorded in England, Wales and - for the first time since 2013 - Scotland and Northern Ireland, BBC Weather said.
The mercury reached 32.6 in Porthmadog, Gwynedd, on Thursday - setting a new record high for 2018.
The hot weather is forecast to continue for most of Britain into next week.
It is the fourth day in a row that the UK has seen its hottest day of the year so far, as temperatures have increased since Monday.
The Met Office has extended its heat warning, which covers parts of England, to last until next Monday.
In the north-west of England, there is an 80% chance of heatwave conditions, it said.
In Glasgow, a temperature of 31C was recorded at 15:00 BST, not quite breaking the longstanding June record for Scotland of 32.2C, last seen in 1893.
There are reports of two roads melting in the heat, with poor conditions on the A920 between Huntly in Aberdeenshire and Dufftown in Moray, while gritters have been sent to the A916 in Fife.
BBC Weather forecaster Billy Payne said Friday would not be as hot but temperatures could reach 29C, most likely in the west of Northern Ireland, western Wales and southern England.
The hot weather is expected to continue for England and Wales on Saturday, he said, while Scotland and Northern Ireland would cool off.
On Sunday, there is a chance of showers and thunderstorms in south-west England, south Wales and possibly Northern Ireland, and temperatures around London could top 30C again.
Public Health England has urged people to look out for the most at risk during the hot weather.
Meanwhile, the RSPCA is urging pet owners to take particular care of their animals in the heat.
In the two weeks to 24 June, they received 625 calls about animals in the high temperatures, mostly dogs in hot cars.
And some rail commuters have faced a week of misery after speed limits were imposed to cope with the high temperatures affecting tracks.
Services on the London Waterloo to New Malden line will continue to be affected by a temporary speed limit from 11:00 BST on Friday.