More than 2,000 people may have died in the UK because of the August heatwave.
The heat may have increased death rates
Statistics released on Friday show there were 2,045 more deaths than usual from 4 to 13 August, during which temperatures were above 30C.
And on 11 August, the day after records were broken as the mercury hit 100F (37.8C), the Office for National Statistics says 1,691 died - 363 more than the average.
But experts say the figures can vary from year to year, and not all deaths might be due to the weather.
Despite the increase, the situation in the UK was not nearly as serious as that in many continental countries.
In France almost 15,000 people died during August, when temperatures remained above 40C for several days.
The elderly were among the worst affected, and in response to the crisis, the French Government announced the creation of 10,000 new health jobs.
The ONS said the shocking deaths in France had triggered its own investigation.
"What happened in Britain was nowhere near that scale but it is very suggestive that there is a link between this very hot weather and the rise in the number of deaths in the UK," said spokesman David Marder.
The number of extra deaths during the August heatwave is still below the winter average, and the ONS said there were often unexplained rises or falls in deaths at any time of the year.
However, there was enough of a correlation to establish a link, the ONS said.
"We can draw a comparison but we are being cautious because the age of people who died and cause of death are not details we have yet," said Mr Marder.
There were an estimated 15,187 deaths over the hottest 10 days in August and 40% of them were in London, the east of England and the South East, where temperatures were consistently highest.
Of the 2,045 extra deaths for that period, compared with the average figure for the past five years, 64% were in these southern areas.
The daily average number of deaths in January over this five-year period is 1,872 - still more than highest number recorded this August.
Initial figures from the ONS for deaths in August, released on 27 August, had suggested 900 more people than normal had died.