The heatwave shows no sign of abating, with forecasters predicting rising temperatures for the weekend in most of Britain.
Temperatures although high, have not yet topped the all-time record
Many places will see a return to Wednesday's temperatures on Saturday - about 35C.
Northern Ireland and western Scotland will miss out on the sunshine, experiencing cloud with some rain in places on Saturday.
But despite the return to higher temperatures, the all-time record - of 37.1C set in 1990 - is not likely to be challenged.
Broadcast meteorologist Alex Deakin, from the BBC Weather Centre, said: "England and Wales will get hotter again throughout the weekend.
"The north west of England may have some showers and on Sunday there is a risk of thunderstorms anywhere in the UK."
The sunshine would last into next week, although not quite as hot, he added.
Wednesday was the hottest day for 13 years with temperatures up to 36.4C, just short of the all-time record.
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It was a few degrees cooler on and Friday, but the continued heat spelt bad news for asthma sufferers, with air pollution rising.
Despite the lasting hot weather, the heatwave should have caused no shortages of water either, thanks to the
occasional showers and unstable weather.
Michael Dukes, of PA Weather Centre, said: "It's not a drought summer like 1995, that's the last time we have had water problems."
Five puppies were discovered dumped in a cardboard box on Tuesday - in temperatures in excess of 32C.
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An RSPCA spokesman said two of the abandoned cross-bred puppies, all about four weeks old, have since
died after they were discovered by a woman walking her dog in a field in Leigh, Greater Manchester.
The spokesman said the dehydrated and underweight puppies were terrified and said the person responsible was "heartless" for leaving the unwanted litter in such hot temperatures.
Air pollution high
Network Rail has said it will impose speed restrictions at noon each day until temperatures drop below 30C.
Smog is making an unwelcome return along with high air pollution levels, caused by sunlight and car fumes.
The air pollution forecast is high for south and central England and Wales. There are also high levels of ozone, which can exacerbate breathing difficulties.
A spokesman for the Department of the Environment said: "Most people will experience no ill effects. Those suffering from lung diseases including asthma, particularly if elderly, should be aware that their symptoms might worsen."
It is estimated the heat could cost Britain's economy almost £300m.
British businesses face massive bills because of absenteeism, falling sales, and transport chaos.
Workers suffering in kitchens, bakeries and foundries are among those who have prompted the TUC to call for a fixed maximum temperature at work, to match the legal minimum.
They want a limit of 30C or 27C for jobs involving strenuous work.
In Scotland, the danger from bush and grass fires is occupying many firefighters.
Strathclyde fire brigade spokesman Rab Coke said the threat of seasonal fires would be greatly exacerbated by the heatwave.