Forecasters are warning temperatures could reach 35C in parts of England on Tuesday as a record-breaking heatwave continues.
On Monday, the UK recorded its all-time highest May temperature as part of London reached 34.8C.
That provisional figure, recorded in Kew Gardens, also surpassed the hottest bank holiday Monday on record - 33.3C in August 2019.
"This heat would be exceptional in the UK even in mid-summer, let alone in May", the Met Office said.
Monday's sweltering conditions are set to be replicated on Tuesday, with forecasters warning slightly warmer air at lower levels could send the mercury even higher.
The highest temperatures are expected in south-east England while other areas in England and Wales will climb to the high 20s.
Fewer places in the north of England will see extreme temperatures compared to Monday.
It will be dry and sunny for most but there will be a bit more moisture in the atmosphere.
There is a chance of thunderstorms across southern England, East Anglia and possibly around Yorkshire.
On Monday, Wales also experienced its hottest May day, reaching 32.2C at Hawarden Airport in Flintshire.
This week's weather means more than half of the monthly record highs - seven out of 12 - have been set since 2003, according to the Met Office.
These exceptionally high temperatures have been caused by "the influence of warmth building under an area of high pressure near the UK", Met Office chief operational meteorologist Dan Suri said.
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.
Scotland and Northern Ireland also recorded their highest temperatures for 2026 so far on Monday - 25.5C in Charterhall and 25.8C at Derrylin in County Fermanagh respectively.
Around 500 properties in Sussex and Kent were left without water, or had intermittent supply due to "increased demand", on Monday afternoon.
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.
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.
The AA has warned drivers "not to drop their guard" when setting out on long journeys this week, with vehicle interiors possibly reaching 60C when in the sun.
"Drivers should never leave children, vulnerable passengers or pets inside a parked vehicle, even for a short time," the breakdown service said.
Age UK recommended staying inside between 11:00 and 15:00, and taking regular cold baths and showers.
Climate change is believed to have played a role in such hot spells as this.
According to the Met Office's State of the UK Climate report, the number of days in the UK with temperatures above 28C has more than doubled and the number of days with temperatures above 30C has more than trebled in the most recent decade, compared with the 1961-1990 average.
"This is what climate change feels like," Hannah Cloke, Regius Professor of Meteorology and Climate at the University of Reading told BBC Radio 4's World At One programme.
