Britons have enjoyed the hottest temperature of the year for the fourth day in a row as the mercury soared past 32C.
Porthmadog in Wales reached 32.6C (90.68F), beating successive highs since Monday as the June heatwave continues.
While the hot weather is set to last, Thursday is likely to see the end of the steadily increasing temperatures, the Met Office said.
Public Health England has issued a warning saying the extreme heat may pose a risk to the most vulnerable.
The rising temperatures have come with warnings to be careful near water and in the countryside, where fire crews have been tackling wildfires.
Elsewhere the body of 13-year-old Ryan Evans, who went missing on Monday after getting into difficulty in Westport Lake in Stoke-on-Trent, was recovered from the water.
The body of a man was also recovered from a lake in Nutfield, Surrey, on Monday.
The RNLI has urged those heading to the seaside to seek out beaches with a lifeguard.
Part of Saddleworth Moor in the Peak District has been gripped by wildfire since Sunday afternoon with the Army helping fire crews who are battling to bring the blaze under control.
Fire chiefs said the situation could go on for weeks, that a wind change could provide more fuel for the fire, and that a “significant downpour of rain” is needed.
A number of homes were evacuated and pockets of fire continue to burn across an area of around 3.7 miles (6km), Greater Manchester Fire and Rescue Service said.
Commuters have endured delays after rail services were forced to impose speed limits due to overheating tracks.
South Western Railway said track temperatures were expected to reach 47C (116.6F) on many parts of its route this week.
Services on the London Waterloo to New Malden line are being subjected to speed restrictions from 11am each day until Friday.
Customers in some areas have been warned to take simple steps to help conserve water.
People can put away garden sprinklers, take short showers instead of baths, and avoid using hoses to clean cars or water the plants in order to reduce demand.
Severn Water has set up bottled water collection points after some parts of Staffordshire and Shropshire saw supplies temporarily interrupted as a result of high demand.
Customers in some parts of the Home Counties have also seen interruptions to supply or low pressure as a result of soaring demand in peak periods, while people served by Southern Water have been warned they may experience low pressure overnight as the network is refilled amid “exceptionally high water demand”.
The hot spell is good news for gardeners, with horticultural experts saying it could help produce excellent vegetables, fruit and flowers.
The Royal Horticultural Society have suggested people use waste water from the kitchen to keep plants nourished and to reduce demand for water.
England’s players and travelling fans will have to contend with cooler conditions in Russia as they take on Belgium in the final group game.
The Met Office forecasts the temperature for Thursday’s match at the Kaliningrad stadium to be 22C (71.6F).
This is the first time in five years that temperatures have hit 30C (86F) in all four nations of the UK, the Met Office said.
“Last year for England there was a warm spell where they had five days over 30C but what makes this current spell different is that it’s nationwide,” meteorologist Bonnie Diamond said.
The weekend and early part of next week promise to remain sunny and warm but easterly winds will bring temperatures down slightly, she said.
She described a forecast earlier in the week for thunderstorms as looking “less likely”.
“There is a small risk of seeing some showers developing in the far south-west but otherwise it will be dry,” she said.
In Cumbria, gritters were sent out onto the roads to try and prevent them being damaged in the hot weather.
The gritters, normally deployed in freezing temperatures, were used to spread crushed rock dust in an effort to stop bitumen road surfaces sticking to tyres in the heat.
Cllr Keith Little, Cumbria County Council cabinet member for highways, said: “If the bitumen becomes overheated, this could potentially lead to a loss of shape in the carriageway surface as well as affecting vehicles.”