The hottest recorded July day has emerged to have been in Wisley, Surrey, where temperatures hit 36.5C (97.7F).
People all over the country are trying to find ways to cool off
Earlier in the day, 36.3C (97.3F) near Gatwick Airport was thought to have been the high.
As the sun blazed across the country schools closed and workers dressed down while the elderly and young children were urged to drink plenty of water.
Peaks were 29.7C in St Angelo, Northern Ireland, 31.3C in Prestwick, Scotland, and 34.2C in Penhow, south Wales.
The previous hottest July day was in 1911, when Epsom, Surrey, reached 36C. The highest UK temperature recorded was 38.5C (101.3F) in Faversham, Kent, on August 10, 2003.
British temperatures this week have exceeded such holiday destinations as Malta, Athens, Bermuda and Rome.
As temperatures soared across the country, the heat brought people to the beaches and into the shade, melted roads and provoked health and safety warnings.
In the heat:
Several schools chose not to open on Wednesday, while others closed at lunchtime and many school sports days were cancelled.
On the roads, emergency measures were brought in to protect surfaces with gritters spreading gravel after the asphalt began to melt. Ambulance service bosses urged drivers in jams to stay with their cars after crews had difficulties getting through to an accident.
Heat caused railway lines to buckle in the Midlands on Tuesday and many services from New Street Station in Birmingham were cancelled. Speed restrictions were in force on the West Coast Main Line.
Unions called for employers to keep staff cool and called for a change in the law to create a maximum working temperature.
Water tankers have been drafted in to top up reservoir supplies in the Midlands and a surge in demand for power for air conditioning systems continued to put pressure on electricity supplies.
Water supplies were affected in Nottinghamshire, Derbyshire and Cardiff while in Shrewsbury 70,000 residents were urged to cut water use as filling pumps failed at a reservoir.
Animals also tried to cool off. At zoos, keepers tried to make life more comfortable for the animals, handing out fruit or blood-flavoured ice lollies. The RSPCA issued warnings about leaving pets in areas without cover or water and said two dogs had died of heat exhaustion.
Visitors to the Peak District National Park in Derbyshire were banned from venturing off footpaths by officials fearing fires in dry woodland areas.
The hot weather brought warnings from climate change experts that the conditions were not unique.
And police warned of other dangers after a 14-year-old boy drowned in a canal in Glen Parva, Leicester as he tried to cool off.
In North Wales, more than 50 people were rescued from a sandbank near a Llandudno beach after they were cut off by the tide.
Forecasters expect a bank of showers coming in from the South West to cool things down on Wednesday night and into Thursday, but the weekend should still be very warm and humidity will be high.
BBC Weather forecaster Rob McElwee said: "Tonight and tomorrow temperatures will be down by four or five degrees for most of us but humidity will be high so it will be more oppressive and hard to keep cool."