What is France's heatwave warning system and how does it work?

France has issued heatwave warnings for half of all mainland counties, including 19 maximum "red alerts". RFI explains how the French system works and what the different alert levels mean in practice.

A traffic light in front of a pharmacy thermometer showing a temperature of 45 degrees Celsius in Nantes, France, on 13 July 2022. © REUTERS / STEPHANE MAHE

Most of the south of France is in the grip of an intense, long-lasting and unusually late heatwave, according to national weather service Météo France, which is forecasting record temperatures of up to 42 degrees Celsius.

Authorities placed 67 of 96 mainland counties, or departments, on heatwave alert throughout Wednesday, including 37 on the second-highest orange alert and 19 on red.

🔴 19 départements en Rouge
🔶 37 départements en Orange et l'Andorre pic.twitter.com/WJX6POkVQt

— VigiMétéoFrance (@VigiMeteoFrance) August 23, 2023

What is France's heatwave alert system?

France's warning system has been in place since 2004. It was introduced in the wake of the country's deadliest heatwave in history, in 2003, which resulted in nearly 15,000 deaths.

That disaster demonstrated the importance of having an early-warning system and clear plan of action when heat begins to pose a public health risk.

• Twenty years after deadly 2003 heatwave, what has France learned?

Every summer since then, France has had a national heatwave plan that sets out what national and local authorities should do in case of dangerous temperatures.

It is built around an alert system that kicks in every year from 1 June and requires authorities to monitor weather and health data daily in order to warn the public as appropriate.

Originally set to last until 31 August, since 2018 the alert period has been extended until 15 September to account for the longer, later summers brought by climate change. 

What do the different alerts mean? 

France has four levels of heatwave warning depending on the risks to public health.

Level One: Green

Every department of France is automatically placed on green alert from June to September. It means that monitoring is underway, but no particular risk has been signalled. Local authorities usually begin public awareness campaigns reminding people of the importance of staying cool and checking on those at high risk.

Level Two: Yellow

This alert indicates a short-lived spike in temperatures that may be dangerous for vulnerable populations such as the elderly or people working outside. Monitoring is stepped up and the various services that would be involved in an emergency response get on standby.

The city of Paris also has its own "heightened yellow" alert, in between levels two and three, when the risk is considered high enough that the council begins calling vulnerable residents to check on them.

Level Three: Orange

Acting on the advice of meteorologists and public health experts, a department's prefect declares an orange alert when a heatwave is forecast.

The exact criteria vary by department, but the danger point is typically when temperatures reach a certain level for three days in row and fail to drop significantly at night; in Lyon, for instance, three days at 35 C and three nights at 21 C triggers an orange alert. Authorities will also take into account factors like air pollution and humidity that could make lower temperatures more dangerous.

A runner jogs past a sign warning of a heatwave in Lyon, on 18 August 2023. © OLIVIER CHASSIGNOLE / AFP

At this point everybody is considered to be at risk, not only vulnerable groups. Each department has its own heatwave response plan, which generally includes measures such as putting nursing homes on an emergency footing, offering extra assistance to homeless people, mobilising social services to check on elderly and disabled people at home, and making designated cool spaces available to the general public.

Level Four: Red

The maximum heatwave alert is only declared in extreme cases – when heat is exceptionally long-lasting, intense and widespread. Such conditions pose a high risk to public health and may also bring collateral problems like drought, power cuts, forest fires and hospitals running out of space.

At this point, the national government gets involved. The prime minister and interior minister are looped in and multiple sectors work together to manage the response. In Paris, for example, a red alert means that the prefect of police takes over emergency efforts, coordinating action on the ground and acting as a liaison with the heads of government.

When a red alert is in place local authorities are allowed to take exceptional measures to avoid health risks, including calling off sporting or cultural events and closing public facilities if needed.

Since it was introduced in 2004, France has declared a red alert for heatwaves six times, all of them in the past four years: twice in the summer of 2019, once in August 2020, another two times in 2022 and now this week.

🔴🌡️ #Canicule | La #VigilanceRouge s'étend à 19 départements pour la journée du 23 août. Les températures devraient avoisiner les 40°C sur presque toute la moitié sud du pays.

Protégez-vous des #FortesChaleurs et suivez les consignes des autorités.

📲 https://t.co/6TsgTrzDyo pic.twitter.com/YvSAhMg94w

— Ministère de l'Intérieur - Alerte (@Beauvau_Alerte) August 22, 2023

Read also:

• French government unveils measures to combat extreme summer weather

• UN warns of more frequent heatwaves into at least the second half of this century