Excess mortality and increased use of emergency rooms can result from extreme heat. These significant health impacts make heat waves a public health issue.

As part of the interministerial directive on heat wave health management in metropolitan France, Santé publique France monitors the impact of extreme heat and implements preventive measures to limit these health consequences.

Health Monitoring of the Impact of Heat Waves

Following the 2003 heat wave, Santé publique France established the Heat Wave and Health Alert System (SACS) in the summer of 2004. This monitoring and alert system aims to identify heat waves likely to have a major health impact, enabling the rapid implementation of measures to prevent and manage the event. Sacs consists of two coordinated components: a meteorological component implemented by Météo-France, and a health component implemented by Santé publique France. The system is evaluated and updated annually.

The main objectives of SACS are as follows:

• anticipate the occurrence of heat waves likely to have a major health impact based on weather forecasts

• identify health impacts during an alert, in order to adapt management measures as needed, particularly for vulnerable populations

• assess the health impact of heat waves at the end of the season.

This Heat Wave and Health Alert System is integrated into the interministerial directive on the health management of heat waves issued by the Ministry of Health.

This national health crisis support and management system, updated annually, aims to outline the organizational procedures implemented to prepare for and manage the health impacts of heat waves, in order to protect the population, particularly vulnerable groups. This system also refers to an ORSEC provision on health management during heat waves intended for departmental prefects.

In practice, the SACS is operational for three and a half months each year, between June 1 and September 15. If specific weather conditions warrant it, it may be activated before June 1 and extended beyond September 15.

Departmental weather forecasts are analyzed daily during the summer by Météo-France. The results of this analysis allow Météo-France to produce the weather alert map, which is released daily at 4:00 p.m. (it may be updated at 6:00 a.m., though this is very rarely the case for heatwave risks, and only to remove departments from the alert at the end of a heatwave episode):

• The yellow weather alert level corresponds to a heat spike: short-term exposure (1 or 2 days) to intense heat posing a risk to human health, particularly for vulnerable or overexposed populations due to their working conditions or physical activity. It may also correspond to a persistent heat episode: high temperatures (biometeorological indicators [IBM] near or below departmental thresholds) that persist over time (more than 3 days).

• The orange weather alert level corresponds to a heatwave: a period of intense heat during which IBMs reach or exceed departmental thresholds for 3 consecutive days and nights, and which is likely to pose a health risk to the entire exposed population.

• The red meteorological alert level corresponds to an extreme heat wave: a heat wave that is exceptional in terms of its duration, intensity, and geographic extent, with a significant health impact on all segments of the population, and which may lead to collateral effects, particularly regarding business continuity.

In the event of an orange or red alert, health monitoring is implemented by Santé publique France to quickly identify any unusual impacts, describe the observed effects, and adapt the management measures to be implemented. During an alert period, reports on the evolution of national and regional indicators are sent to health authorities, and a comprehensive report is produced at the end of the year.

Preventing the Health Impacts of Extreme Heat

The heatwave prevention system

Santé publique France leads the prevention program in collaboration with the Ministry of Health and Prevention. This program aims to raise awareness of recommended actions and warning signs to protect the population from the health consequences of heat waves. It targets the entire population and, in particular, those vulnerable to heat due to their age (older adults and young children), their health status (medications that amplify the effects of heat or disrupt the body’s ability to adapt to heat), a life event (pregnant women), or due to overexposure to heat resulting from living conditions, work environments, or individual behaviors (residents of homes exposed to extreme heat, athletes, workers, etc.).

The prevention plan has two components:

Outside of heat wave periods

Prior to the seasonal watch, information is disseminated to institutional and local stakeholders (Regional Health Agencies, prefectures, municipalities, etc.), as well as to healthcare professionals, early childhood care providers, caregivers for the elderly, and tourism professionals, through the distribution of available printed materials:

• posters on recommended actions and warning signs, as well as a 4-page brochure, available in English;

• “Guidelines for Your Practice” are made available to healthcare professionals to assist them in caring for patients particularly vulnerable to heat: children, vulnerable adults, and the elderly.

Since 2023, prevention messages aimed at older adults and/or those taking medication have been distributed as close as possible to the public, particularly in pharmacies and waiting rooms at healthcare facilities (health centers, university hospitals) during the monitoring period.

The tools and documents produced by Santé publique France are available in the TOOLS tab.

During a heat wave

• During periods of an orange heat wave alert covering a limited geographic area, the response is stepped up: social media is utilized (advertising space is purchased) with messages tailored to the target population (adults, parents of children, and older adults).

• During periods of orange or red heatwave alerts covering most of the country, radio and TV spots are broadcast via media requisition by decision of the Ministry of Health.

The heatwave adaptation plan for the 2024 season

Since 2023, the heatwave adaptation plan, led by Santé publique France, aims to encourage the public to incorporate health-promoting behaviors into their daily lives as soon as temperatures rise, rather than only during heatwaves. In its initial phase, the heat-vulnerable populations targeted are people living in heat-exposed housing and unsupervised “athletes.”

The initiative includes:

• a website, vivre-avec-la-chaleur.fr, which offers a range of advice and tips in the form of animated videos and articles on how to adjust one’s lifestyle as soon as temperatures rise. For example:

  • well before temperatures rise: install sunshades around the home or identify cool places near your home;

  • when it’s hot: optimize the use of a fan or the opening and closing of windows, adjust your exercise routines...

• radio segments featuring "expert advice" that highlight tips and advice from the vivre-avec-la-chaleur.fr website.

These tools are promoted through multimedia campaigns (social media, radio, digital displays in public spaces, etc.) that begin in May and run throughout the summer.

Learn more

• Ministry of Solidarity and Health / Heat Waves and Extreme Heat

• French National Agency for Medicines and Health Products Safety (ANSM), “Heat Waves and Health Products” section

• Météo-France

• Météo-France heat advisory map (updated at 6 a.m. and 4 p.m.) and Météo-France recommendations based on heat advisory levels

• National Institute for Research and Safety (INRS), “Working in the Heat” section

• Heat Wave Info Service: "Heat Wave Info Service" hotline 0 800 06 66 66 (toll-free) available daily from 9 a.m. to 7 p.m.