TL;DR
The UK has set a new record for the hottest May day, with temperatures reaching 34.8C in London. Wales also recorded its hottest May day at 31.1C in Trawscoed, Ceredigion.
The UK has recorded its all-time highest May temperature as parts of London reached 34.8C on Monday.
That figure, recorded in Kew Gardens, also surpassed the hottest Bank Holiday Monday on record - 33.3C seen on the August bank holiday in 2019.
Wales has also experienced its hottest May day, reaching 31.1C at Trawscoed, Ceredigion.
And the mercury is expected to rise further in the South and South East of England, with forecasters warning of possible 35C heat on Monday and Tuesday.
The UK recorded its warmest May night on Sunday, with highs of 19.4C in London.
The average temperature for the end of May is 14-20C.
On Friday, the UK Health Security Agency issued its first amber-heat health alert of 2026, covering much of England, including the West Midlands, East Midlands, East of England, South East and London.
The North East, North West, South West, Yorkshire and Humber regions are under a yellow alert. Both alerts will remain in place until 17:00 BST Wednesday.
BBC lead weather presenter Simon King has described this early-season heatwave as unprecedented.
Scotland and Northern Ireland recorded their highest temperatures for 2026 so far on Monday - 25.5C in Charterhall and 24.6C in Hillsborough respectively.
Around 500 properties in Sussex and Kent were left without water, or had intermittent supply due to "increased demand", on Monday afternoon.
Apologising for the disruption, South East Water said it was working "as quickly and safely as possible" to resolve the issues.
Across the UK a number of bank holiday events were cancelled because of the extreme heat.
In Surrey, Leatherhead Lions Club said its annual bank holiday donkey derby would no longer include the donkeys or a dog show "for the welfare and comfort of the animals".
Despite these cancellations, thousands of people gathered in the baking heat to watch competitors from all over the world battle it out at the Gloucestershire cheese-rolling race.
German YouTuber Tom Kopke, known online as Tooleko, beat local competitor and Guinness World Record holder Chris Anderson in the first race of the annual event on Cooper's Hill in Brockworth.
As the hot weather continues, England could see some thunderstorms on Tuesday evening, forecasters have said.
Temperatures are expected to hit 30C on Wednesday and Thursday in England and Wales before dipping into the high 20s on Friday.
Heatwave conditions were met in eight parts of England on Sunday - Heathrow in Greater London, Benson in Oxfordshire, Brooms Barn in Suffolk, High Beech in Essex, Kew Gardens and Northolt in London, Santon Downham in Suffolk and Writtle in Essex.