The UK has recorded the hottest day of the year so far as the Met Office said there was a provisional temperature of more than 33C measured in Surrey.
As well as the 33.2C high in Charlwood, temperatures of 26.9C were provisionally recorded in Bute Park in Cardiff and 27.2C in Aviemore in the Highlands, the weather service said on Saturday afternoon.
Parts of the country will see the “perfect conditions” for thunderstorms as the heatwave continues, according to the forecaster.
A yellow warning for thunderstorms covering parts of south-east Scotland, Yorkshire, the Midlands and Wales has been issued by the Met Office as it said there could be frequent lightning, large hail, strong winds and heavy rain in the affected areas.
Up to 40mm of rain could fall in less than two hours, the forecaster said, as it urged those in the warning areas to consider whether their location is at risk of flash flooding and to prepare accordingly.
The alert, which includes Manchester, Derbyshire and Newcastle upon Tyne, is in place from 5pm on Saturday until 3am on Sunday.
In an online forecast, Met Office meteorologist Jonathan Vautrey said: “Provisionally, Northern Ireland has recorded its warmest June night on record, Friday into Saturday, and this hot and humid air is being dragged up a little bit from parts of continental Europe, but we also have low pressure out in the Atlantic, and that is driving weather fronts across the UK, providing instability in the air and the perfect conditions to start sparking off some thunderstorms as that hot and humid air rises rapidly.”
As Saturday continues there may be “sharp showers” heading north, accompanied by “a few rumbles of thunder” during daylight hours with “sunny spells” in between, he added.
“Both Wales, Northern Ireland and Scotland all recorded their warmest day of 2025 yesterday.
“For the latter two, it is going to be a slightly less warm day today, a touch fresher, but still certainly around the mid 20s is possible for parts of Northern Ireland and into central areas of Scotland,” Mr Vautrey said.
An official heatwave is recorded when areas reach a certain temperature for three consecutive days, with thresholds varying from 25C to 28C in different parts of the UK.
“Many places” in England and “one or two areas” in Wales, including Cardiff, entered a heatwave following Friday’s highest temperatures, Becky Mitchell, meteorologist at the Met Office, said.
An amber heat-health alert, issued by the UK Health Security Agency (UKHSA) for the first time since September 2023, for all regions in England remains in place over the weekend.
The agency has warned that significant impacts are likely across health and social care services, including an increase in demand, during the alert period.
Sunday will see a day of “sunny spells and showers” with highs of around 27C and 28C, Met Office weather forecaster Dan Stroud said.
Conditions are expected to feel “a lot fresher” in the west of the UK whilst remaining “very warm and humid” in the east, he added.
“For the vast majority of the country, the temperature is going to be much, much closer to the mid, late June average.
“As we move our way through Sunday night into Monday, it’s going to feel a lot fresher for us all, a lot more comfortable sleeping conditions.”
Temperatures reached 32.2C in Kew, west London, on Thursday while Friday saw highs of 30.8C recorded in both England and Wales.
Ireland’s hottest temperature for almost three years of 29.6C was recorded on Friday in Mount Dillon, Co Roscommon, Irish forecaster Met Eireann said.
Pharmacies have advised their patients to store medicines safely as the heat-health alert continues, adding that most medicines kept at room temperature should be stored in a cool, dry place, away from direct sunlight and hot areas, the National Pharmacy Association (NPA) has said.
Warmer temperatures may lead to some medicine losing its effectiveness or unwanted side effects, the NPC added.
The hot weather comes as thousands of people watched the sunrise over Stonehenge in Wiltshire to celebrate the summer solstice on Saturday, marking the year’s longest day.
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