An 18-month-old baby has died after being left in a car during a 40C heatwave in France. Firefighters discovered the child in the car park of a university medical campus, where he was unconscious and suffering from hyperthermia.

He was taken to La Timone Hospital in Marseille, where he sadly died on Tuesday. The baby's parent reportedly forgot he was in his car on the way to work, according to French outlet BFM. It marks the fourth death of a child in a hot vehicle during this week's heatwave in France.

Paris hitting a June record of 40.9C on Wednesday, the first time in 150 years that it's exceeded 40C.

The city's mayor, Emmanuel Gregoire, said the heatwave disrupted power supplies and shut schools and cultural landmarks.

He told TF1: "The profile of people currently facing health risks is not necessarily what one might expect - that is, the most vulnerable, because they are closely monitored and well informed.

"Rather, it’s people aged between 50 and 70 who are generally in good health, but who think this is just a normal period and continue going about their usual activities as if nothing has changed. Really, protect yourselves."

The exact number of heat-related deaths in France is not yet known, but authorities said earlier this week that 48 people had died just from drowning.

Prime Minister Sebastien Lecornu activated the highest level of health services mobilisation, meaning non-urgent operations could be cancelled to focus on weather-related emergencies.