What to Do During Extreme Heat

During extreme heat, stay in a cool or air-conditioned space, drink water regularly even without feeling thirsty, avoid strenuous activity between 10am and 4pm, wear light clothing, close shutters during the day, and check on elderly or isolated neighbors. If someone shows confusion, a very high body temperature, or loses consciousness, call emergency services immediately, since this may be heat stroke.

Extreme heat is not just an inconvenience. It is one of the deadliest weather hazards in the world, and it is becoming more frequent across France and much of Europe. If you are searching for what to do during extreme heat, you likely already know a heatwave is on the way or already underway. This guide walks through the exact steps to protect yourself, your family, and the people around you until the temperatures drop.

What Counts as Extreme Heat?

Extreme heat refers to a period of unusually high temperatures, often combined with high humidity, that lasts for at least two to three consecutive days. Your body has to work much harder than normal to stay at a safe internal temperature during extreme heat, and that strain can quickly turn dangerous, especially for older adults, young children, pregnant women, and people with chronic health conditions.

Temperature alone does not tell the whole story. The World Health Organization notes that humidity, wind, and sun exposure combine with air temperature to determine how much heat stress the human body actually experiences, which is why heat index and wet bulb temperature (a measure combining heat and humidity) are often better predictors of danger than the thermometer reading alone. A high heat index or elevated UV index on top of already extreme heat compounds the risk, since the body loses its ability to cool itself through sweat evaporation once humidity climbs too high.

France has direct, recent experience with this kind of extreme heat. The June 2026 heatwave was more intense than any previously recorded in mainland France and Corsica, surpassing even the historic August 2003 episode, with June 24 and 25 becoming the hottest days ever recorded nationally. Paris crossed 40°C on both of those days, a threshold the capital has only exceeded five times since record-keeping began in 1947. Extreme heat is no longer a rare summer event in France. It is a recurring risk that deserves a real plan.

If you want a broader foundation before diving into today's action steps, our guide on How to Stay Safe in Heatwaves and Extreme Heat covers the full picture of preparation and recovery from extreme heat.

Step 1: Check Official Alerts Before You Do Anything Else

Before deciding what to do during extreme heat, check the current alert level. In France, Météo-France issues a color-coded vigilance map for canicule (heatwave) risk, ranging from green to red. A red "canicule extrême" vigilance level indicates an exceptional extreme heat episode marked by its duration, intensity, timing, or geographic extent. When that level is triggered, even young, healthy people can suffer heat stroke or serious illness during extreme heat if they do not take precautions.

If you need guidance rather than just a forecast, France operates a free hotline for exactly this purpose. The "Canicule info service" green number, 0800 06 66 66, is open from 9am to 7pm across mainland France to offer advice on protecting yourself and those around you during extreme heat, particularly the most vulnerable. Save that number in your phone before the next episode arrives, not during it.

Step 2: Take Immediate Cooling and Hydration Action

Once you know extreme heat is active or forecast, act early rather than waiting for symptoms to appear.

• Drink water regularly, even before you feel thirsty. The CDC recommends drinking plenty of fluids throughout an extreme heat episode, even without an urge to drink, since people suffer heat-related illness when their bodies are unable to properly cool themselves.

• Limit outdoor activity during the hottest window of the day, generally between 10am and 4pm, and shift errands, exercise, or work to early morning or evening.

• Wear loose, lightweight, light-colored clothing and use sunscreen if you must be outside, since sunburn reduces your skin's ability to release heat and a high UV index adds extra strain during extreme heat.

• Take cool showers or baths to actively lower your body temperature rather than relying on a fan alone. According to the American Red Cross, electric fans should not be relied on as a sole cooling strategy once temperatures reach the high 90s Fahrenheit (roughly 35°C and above), because they can create a false sense of comfort without actually preventing heat illness.

• Spend a few hours in an air-conditioned space if you can. If your home has no air conditioning, identify the nearest cooling center, shaded park, library, or shopping mall in advance.

Step 3: Keep Your Home as Cool as Possible

Even without air conditioning, you can meaningfully lower indoor temperatures during extreme heat with a few consistent habits:

1. Close shutters, blinds, and curtains during the day, especially on windows that face the sun.

2. Open windows in the early morning and late evening when outdoor air is cooler, and close them again once temperatures rise.

3. Avoid using the oven or other heat-generating appliances during peak hours.

4. Use damp cloths or a light spray of water on your skin combined with airflow to encourage evaporative cooling.

5. Move to the coolest room in the house, typically one on a lower floor with limited sun exposure, especially at night.

French health authorities in heavily affected regions specifically recommend this pattern of shutting the home during the day. During the June 2026 red alert in Charente, the prefecture directly advised residents to keep their homes cool by closing shutters, curtains, and windows during the day.

Step 4: Protect the People Most at Risk

Extreme heat does not affect everyone equally. During France's red vigilance episodes, authorities repeatedly emphasize checking on people over 65, people with disabilities, and those who are isolated or overexposed, including people experiencing homelessness.

Practical actions include:

• Calling or visiting elderly relatives and neighbors at least once a day during extreme heat.

• Never leaving children or pets alone in a parked car, even for a few minutes.

• Registering vulnerable or isolated individuals on municipal support lists where available, since town halls mobilize resources such as mapped cooling spots and extended hours at green spaces and municipal pools during these episodes.

• Watching outdoor workers and athletes closely, since this group faces particular risk of dehydration and heat stroke during extreme heat.

If your household includes anyone in a high-risk category, our companion article What to Do During a Heatwave? Essential Safety Tips goes deeper into building a personalized protection plan for elderly or medically vulnerable family members.

Step 5: Know the Warning Signs of Heat-Related Illness

Extreme heat can escalate from mild discomfort to a medical emergency quickly. According to France's regional health agency in Grand Est, warning signs include a change in usual behavior, significant weakness or fatigue, unusual difficulty moving, headaches, dizziness, confusion or even convulsions, nausea, vomiting, diarrhea, intense thirst, muscle cramps, a body temperature above 38.5°C, and unusual nighttime restlessness.

These symptoms fall into two categories, and knowing the difference matters because the response is different:

Heat exhaustion is the body's response to an excessive loss of water and salt, usually through excessive sweating, and it generally improves with rest, fluids, and cooling. Heat stroke is far more severe and can involve confusion, loss of consciousness, and a dangerously high core temperature. Heat stroke is always a medical emergency during extreme heat, not a wait-and-see situation.

Step 6: What to Do If Someone Shows Signs of Heat Stroke

If you suspect heat stroke in yourself or someone nearby during extreme heat, act immediately rather than waiting to see if symptoms improve.

1. Call emergency services right away. In France, that means dialing 15 for SAMU or 112, the European emergency number, in case of fainting, disturbed behavior, dizziness, severe headaches, extreme fatigue, nausea, or muscle cramps.

2. Move the person to a cool, shaded, or air-conditioned area if possible.

3. Remove excess clothing to help the body release heat.

4. Apply cold, wet cloths or ice packs to the head, neck, armpits, and groin, following Ready.gov's guidance for treating suspected heat stroke while waiting for help to arrive.

5. Stay with the person until emergency responders arrive, and do not leave them alone.

Every minute matters here. Heat stroke can cause permanent organ damage or death if the body's core temperature is not brought down quickly.

This guidance is for general safety awareness during extreme heat and does not replace professional medical advice. Always call local emergency services for a suspected medical emergency.

Step 7: Adjust for Work and Outdoor Activity During Extreme Heat

If you cannot avoid working or exercising outdoors during extreme heat, build in deliberate recovery time. The CDC's occupational heat stress guidance recommends limiting time in the heat and increasing recovery time spent in cool areas, along with frequent hydration breaks and a buddy system so coworkers can watch for early warning signs in each other. If you supervise a team, this is also the moment to activate a heat alert protocol tied to the local forecast rather than waiting for someone to feel unwell during extreme heat.

Final Thoughts

Extreme heat rewards preparation and quick decision-making far more than it rewards toughing it out. Check the forecast and local vigilance level before your day starts, hydrate before you feel thirsty, keep your living space shaded and ventilated at the right hours, and never underestimate warning signs in yourself or people around you. For a complete look at longer-term preparation, home adjustments, and household emergency plans, revisit How to Stay Safe in Heatwaves and Extreme Heat and What to Do During a Heatwave? Essential Safety Tips for the next layer of protection against extreme heat.