Nearly 1,700 additional people died during the heatwave two weeks ago that saw temperatures top 40C in the UK for the first time in recorded history.
Records were broken last month after a new record-high temperature of 40.3C was recorded at Coningsby, Lincolnshire, on 19 July.
Much of England and Wales was placed under the nation's first ever “red” extreme heat alert with warnings of the potential for serious illness and a danger to life.
The record was broken three times in a few hours with 39.1C measured in Charlwood, Surrey and 40.2C at Heathrow Airport.
Figures released by the Office for National Statistics on Tuesday reveal there were 1,680 excess deaths in the week ending 22 July - a rise of 18.1% compared to the previous five years.
Experts have, however, warned that the figures should not be regarded as a definitive account of how many people died as a direct consequence of the heat.
Sarah Caul, Head of Mortality Analysis at the ONS, warned the numbers "do not tell the full story".
"There are always individual days on which the number of deaths exceeds the five-year average for that day and some of these coincide with dates when parts of the country were experiencing extreme temperatures, whether cold or hot," she said.
"In 2019, for example, the recorded temperature in Cambridge was 38.3 Celsius on 25 July. Looking at the deaths in England and Wales at that time, we reported an increase in deaths on that day and shortly after. This was followed by a subsequent drop in the number of deaths, which tends to happen after a period of excess mortality.
"Among the most common causes of death, including in the summer months, are conditions such as respiratory failure, heart disease and Alzheimer’s. It is likely that some of these deaths are hastened by circumstances associated with extreme heat, but the death certificate would not necessarily describe the death as “heat-related”, unless the person certifying the death specifically mentions the heat."
But even this, Caul says, is not necessarily indicative they died because of the heatwave.
If, for example, a death record gives the cause of death as “drowning”, we are unlikely to know that the deceased went swimming because of the extreme heat," she cautioned.
"It is difficult to attribute that individual death to the heatwave."
The heat also put pressure on the fire services, who battled grassfires and buildings ablaze throughout the heat.
A total of 16 homes were lost on 19 July in the large fire in Wennington, east London, and fire crews had to fight to save the fire station itself, located nearby, from the flames.