• anticipate the occurrence of heat waves that could have a major impact on public health based on weather forecasts;
• identify health impacts during an alert in order to adjust management measures as needed, particularly for vulnerable populations;
• assess the health impact of heat waves at the end of the season.

This national framework for health crisis support and management, 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 public, particularly vulnerable populations. This framework also refers to an ORSEC provision on the health management of heat waves intended for departmental prefects.

In practice, the SACS is operational for three and a half months each year, from June 1 to 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 enable Météo-France to produce the weather watch map, which is released daily at 4:00 p.m. (it may be updated at 6 a.m., although this is very rarely the case for heat wave risks, and only to remove departments from the alert list at the end of a heat wave episode):

• A yellow weather alert corresponds to a heat spike: short-term exposure (1 or 2 days) to intense heat posing a risk to human health, particularly for vulnerable populations or those overexposed 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 heat wave: a period of intense heat during which BMIs reach or exceed departmental thresholds for 3 consecutive days and 3 consecutive 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 secondary effects, particularly in terms of business continuity.

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

Santé publique France leads the prevention initiative, in collaboration with the Ministry of Health and Prevention. This initiative aims to raise awareness about the precautions to take and the warning signs to watch for in order to protect the public from the health consequences of heat waves. It targets the entire population and, in particular, those who are vulnerable to heat due to their age (older adults and young children), their health status (medications that increase the effects of heat or interfere with 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 behavior (residents of homes exposed to extreme heat, athletes, workers, etc.).

Outside of heat wave periods

Prior to the seasonal watch, information is disseminated to institutional and local authorities (Regional Health Agencies, prefectures, municipalities, etc.), as well as to healthcare professionals, early childhood educators, caregivers for the elderly, and tourism professionals, among others, by distributing the following 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 who are particularly vulnerable to heat: children, vulnerable adults, and older adults.

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 an orange heat wave alert covering a limited geographic area, the response is stepped up: social media is utilized (through purchased ad space) with messages tailored to the target population (adults, parents of children, and older adults).
• During an orange or red heat wave alert covering most of the country, radio and TV spots are broadcast under a media requisition ordered by the Ministry of Health.

Since 2023, the heatwave adaptation program, led by Santé publique France, has aimed to encourage the public to incorporate health-promoting behaviors into their daily lives as soon as temperatures rise—and not just during heat waves. In its initial version, the heat-vulnerable populations targeted are people living in heat-exposed housing and unsupervised “athletes.”

The program 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 spots near home;
  • when it’s hot: make the best use of a fan or opening and closing windows, and adjust your exercise routine...;
• 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.

Several observations have prompted these reflections:  

• Heat waves are becoming more frequent, occurring earlier in the year, and more intense, with numerous and often serious health consequences (exacerbation of chronic conditions, workplace accidents, learning difficulties in school, premature births, use of emergency care, and mortality) despite the preventive and protective measures implemented each summer

• Data has been available for over 20 years, but its use remains limited or suboptimal. Public health challenges fall under the purview of stakeholders who do not always have the necessary tools to act effectively.

• The urban environment and built-up areas exacerbate these risks: for example, the risk of death among seniors is four times higher when they live in attics and two to three times higher when they live in neighborhoods that are the hottest at night (2003 data).

• Greening could prevent 80 to 300 deaths per year, according to a quantitative assessment conducted in the metropolitan areas of Montpellier, Lille, and Rouen from 2015 to 2017.

• On average, people spend 80% of their time indoors (at home, school, work, recreational facilities, healthcare facilities, etc.), where buildings can serve as a refuge if they are sufficiently cool.

URBACS aims to integrate health considerations into urban planning and construction/renovation projects by:

• Contributing to the training and awareness-raising of professionals (architects, urban planners, elected officials, etc.) regarding the health impacts of heat through up-to-date data and tools that facilitate their understanding and dissemination to maximize the effectiveness of decisions.

• Bringing together stakeholders from the fields of health, construction, urban planning, and climatology

• Tailoring its actions to address challenges at both the national and local levels

UrBaCS’s initiatives thus help promote the design of buildings and neighborhoods that are resilient to heat, in order to better protect all populations—particularly the most vulnerable and those in the most precarious situations—from the health effects of heat.

• To join the network or get more information: urbacs@santepubliquefrance.fr.