The number of deaths spiked on the hottest day of the summer, provisional official data shows.
There were 1,473 deaths on July 25 registered in England and Wales, rising from about 1,100-1,200 deaths per day around the same time, according to figures from the Office for National Statistics (ONS).
July 25 saw temperatures reach 38.7C in Cambridge, breaking the record for the highest temperature ever recorded in the UK.
The ONS was looking at whether "killer heatwave" news headlines are backed up by the data in a release called 'Do summer heatwaves lead to an increase in deaths?'
The stats body cautioned that the May to August 2019 data is "highly provisional" due to the amount of time it can take for deaths to be registered, meaning the recorded number of deaths per day is likely to increase as more deaths are registered.
While comparisons with previous years cannot yet be made using the recent summer's data, the statisticians compared the number of deaths per day in summer 2018 with the five-year average (2013-18).
The ONS said: "The comparatively high number of deaths occur mainly on days that are defined as heatwaves by Public Health England (PHE) in their deaths relating to heatwaves report."
These spikes tended to be followed by periods of lower-than-average deaths, the ONS said.
The body went on: "This means that at a daily level, extreme heat seems to have an impact on the number of deaths, but across the summer period as a whole the number of deaths is similar to previous years.
"This could be because the most vulnerable people, for example, those with pre-existing respiratory or cerebrovascular diseases are more susceptible to death during heatwaves."
Even when taking into account the heatwaves, the effects of winter on mortality are consistently greater than summer, it added.