The sweltering weather is set to continue on Saturday, as September’s unprecedented heatwave peaks.
Thursday was the warmest day of 2023 yet, with 32.6C (91F) recorded in Wisley, Surrey.
The Met Office says temperatures could reach almost 33C on Saturday, making it the sixth consecutive day of the mercury exceeding 30C.
However, it may be the last hot day for some areas of England and Wales, with a warning of possible thunderstorms.
It comes as figures published by NHS England show there has been a fivefold increase in the number of people seeking advice about heat exhaustion over the past week.
The current heatwave is the longest run of 30C September days on record.
Met Office spokesman Stephen Dixon said the hot spell would continue over the weekend, especially in south-east England, but thunderstorms were expected in some parts.
A yellow alert for heavy showers and thundery downpours is in place from 14:00 BST to 21:00 for central England and eastern Wales.
Some areas could see 30-50mm of rain, with “a possibility of hail and lightning”, Mr Dixon said.
“There’s a bit of a weather breakdown on the way. Some might see thundery rain but it will stay hot.”
Friday’s provisional highest temperature was set at 30.9C in Cavendish, Suffolk, according to the Met Office.
In Northern Ireland, Friday was the hottest September day on record, with 28C recorded at Castlederg in County Tyrone, breaking the previous peak set in Armagh in 1906.
And it was 28.8C in Bishopton in Glasgow on Friday, as temperatures in the mid to high 20s were recorded in Scotland.
Heat exhaustion queries
Meanwhile, an amber heat-health warning issued by the UK Health Security Agency is in effect for nearly every area of England until 21:00 on Sunday.
This indicates that the effects of high temperatures could be felt across the whole health service.
Prolonged heat above 30C is a risk for older people and those with respiratory or cardiovascular diseases.
The rise in temperatures has led to a 552% increase in people visiting the NHS website for heat exhaustion advice.
There were 32,130 visits to the health advice page on heat exhaustion and heatstroke from Sunday to Thursday this week, according to figures released by NHS England, which runs the NHS website.
There were 4,928 visits made during the same period last week.
Heatwaves have become more frequent, more intense, and last longer because of human-induced climate change.
Last year the UK recorded temperatures above 40C for the first time. Scientists said that would have been “virtually impossible without climate change”.
The world has already warmed by an average of 1.1C since the industrial era began and temperatures will keep rising unless governments around the world make steep cuts to greenhouse gas emissions.