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What is a heatwave and when does it become dangerous?
In France, a heatwave is officially declared when temperatures exceed thresholds defined by Météo-France for at least three consecutive days, both day and night. This phenomenon is particularly feared because the night no longer allows the body to recover from the heat accumulated during the day.
The deadliest episodes occur when nighttime temperatures remain above 20 or 25 degrees Celsius, leaving the body no respite. The human body is then forced to work tirelessly to maintain its internal temperature around 37 degrees, which can quickly become exhausting, even fatal.
The main health risks of the heatwave
Dehydration: a silent danger
In hot weather, the body sweats more to cool down. This water loss can quickly lead to dehydration , especially if the person doesn't drink enough. The first signs are a dry mouth, dark urine, headaches, and unusual fatigue. Without sufficient fluid intake, the situation can progress to mental confusion, muscle cramps, and a drop in blood pressure.
Heatstroke: an absolute emergency
Heatstroke is the most serious complication associated with a heatwave. It occurs when body temperature exceeds 40 degrees Celsius and the body's thermoregulation mechanisms are overwhelmed. Symptoms include hot, dry skin (the body has stopped sweating), mental confusion, seizures, and loss of consciousness. It is an absolute medical emergency requiring immediate contact with emergency services (15 in France).
The most vulnerable people
Certain populations are more exposed to the effects of heat:
- The people over 65whose sensation of thirst is often diminished
- The infants and young childrenwhose thermoregulation is not yet mature
- The people suffering from chronic illnesses (cardiac, renal, respiratory)
- The people undergoing certain drug treatments (diuretics, antidepressants, antipsychotics)
- The outdoor workers and athletes exposed to the sun for several hours a day
Practical tips for protecting yourself from the heatwave
Stay properly hydrated throughout the day
The golden rule during a heatwave: drink water regularly , even if you're not thirsty. Health authorities recommend consuming at least 1,5 liters of water per day, and more in cases of intense heat or physical activity. Avoid alcohol, sugary sodas, and excessive coffee, which promote dehydration. Light broths, cold herbal teas, and fruit-infused water are excellent alternatives for varying your fluid intake.
Adapting one's environment and habits
During a heatwave, managing your indoor environment is crucial:
- Close shutters and windows in the morning as soon as the outside temperature exceeds the inside temperature
- Ventilate at night or early in the morning when the outside temperature drops
- Use a a fan or an air conditioner in moderation (do not exceed 8 degrees difference with the outside)
- Take cool showers or baths several times a day, without drying yourself completely
- Wear light, loose-fitting, and light-colored clothingpreferably in cotton or linen
Avoid going out during the hottest hours
Between noon and 4 p.m., the sun's rays reach their peak. It is strongly advised to stay indoors or in a cool place during these hours. If you must go out, wear a wide-brimmed hat, apply SPF 50 sunscreen, and always carry a bottle of water with you. Tree-lined parks, air-conditioned shopping centers, and cooled community halls are valuable havens during periods of intense heat.
Looking out for those around you
Solidarity is an effective weapon against heatwaves. Remember to call elderly people in your community regularly, especially if they live alone. In France, town halls maintain a heatwave register that allows vulnerable people to report their situation and be contacted in the event of a heatwave. Don't hesitate to register your loved ones or yourself if necessary.
Useful numbers and resources in case of a heatwave
In case of severe symptoms or if you have any doubts, do not delay in contacting emergency services:
- SAMU : 15 (medical emergencies, heatstroke)
- firefighters : 18
- European emergency number : 112
Conclusion: the heatwave is prepared for and experienced together
Heat waves are an increasingly frequent and intense climatic phenomenon due to climate change. While they pose a real danger, especially for vulnerable populations, taking the right steps can significantly limit their effects. Hydration, staying cool, checking on loved ones, and knowing the warning signs are your best allies. Never underestimate a heat wave and don't hesitate to call emergency services if you have any doubts.
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