During the heatwave in France in August, there were almost 400 heat-related deaths in the affected departments, according to estimates by the French public health authority.
Seniors 75 and older were most affected, it said in a report published in Paris on Wednesday.
During the third heatwave of the summer in France, between August 11 and August 26, 5.4% more people died than in comparable weeks in previous years without high temperatures.
During this period, temperatures in France rose to 42 degrees Celsius in some regions.
If more people die in weeks with high temperatures than in comparable weeks in other years, this excess mortality is assumed to be heat-related. However the results are preliminary, it said.
Although most of the heat-related deaths were due to pre-existing conditions, the heat put additional strain on the body.
The results show that heat is a health risk, even outside of heatwave periods, which requires the implementation of prevention measures to reduce the impact of heat on the population, the report stated.
A final report is expected in the autumn.
