France is heading into its fifth heatwave of the year, with Meteo-France placing 43 departments under orange alert from Tuesday, August 11, because of intense heat. The episode is expected to last until the end of the week, following a record-hot July and two earlier heatwaves in May and June.
Dr Jeremy Monteiro, a hospital physician with the Samu emergency service in Bouches-du-Rhone and at the Timone university hospital in Marseille, and a board member of Samu-Urgences de France, spoke to TF1info about how the body copes with repeated extreme heat.
How the body responds
Monteiro said the body adapts to rising temperatures through sweating and cardiovascular changes that keep body temperature near 37 degrees Celsius. He said heatwaves recurring over a short period place greater strain on these defence mechanisms, which are not unlimited, and this can have serious effects, particularly for the most vulnerable people.
Monteiro said the body's adaptation to heatwave episodes remains limited.
Short-term and delayed effects
He distinguished between acute effects of heat, such as dehydration, heatstroke and fainting, which can occur in the first hours of a heatwave, and longer-term effects that appear seven to ten days later. He said patients with respiratory conditions can suffer respiratory, cardiac or kidney decompensation, meaning organs function less well.
Monteiro explained that a tired kidney filters water, sodium and potassium less effectively, risking dangerous buildup in the body that can become life-threatening in the short term. He compared the heart to a pump sending oxygen to cells, saying that when it malfunctions, cells do not get enough nutrients to function properly.
Limited adaptation over time
Monteiro said the body does have mechanisms to adapt to both heat and cold, but adaptation to repeated heatwaves stays limited, since such frequent episodes leave much shorter recovery periods. He said that in hot countries, prolonged heat exposure has allowed bodies to adapt at a cellular level, but France is meant to have a temperate climate, not such regular extreme heat, so people are not immune to it.
How to protect yourself
Monteiro reiterated official recommendations: drink water regularly, cool down, avoid sun exposure especially in the afternoon, reduce physical effort, and check on vulnerable people. He said anyone suffering heatstroke should not hesitate to contact their doctor or call the Samu emergency line on 15.
