The BBC's Paris correspondent Hugh Schofield described people scurrying for shade "as if it was the middle of August" in the French capital, with temperatures reaching 34C (93.2F) on Tuesday.
This comes as France's national weather service said a "heat dome" settling over Western Europe was producing temperatures 10 to 15 degrees Celsius above the average for May.
A tourist told the BBC he chose May to visit Paris in order to avoid the summer months.
'We know it can be really bad in June, July, August, and I'd thought that if we came up in May, it'd be a bit easier', said Brent visiting from Australia.
