Heat wave: when was the last in France?

[Mise à jour le 29 avril 2022 à 17h54] L’India knows since March 2022 an unprecedented heat wave with temperatures approaching 50 degrees at the end of April. Pakistan is also affected by this heat wave. In France, the risk of a heat wave begins at the end of June usually. Since 2015, the heat waves have increases in frequency and intensity in France with an occurrence earlier (in June) or later (late August-early September) during the summer period. Among the main heat waves in June in Francethose of june 19471976, 20032005, 2006 and closer 2017 and 2019. The elderly are very vulnerable to high heat and special attention should be paid to them.

Word “heat wave” comes from the Latin “canicula” which means “little female dog”. Canicula is the name given to the star Sirius (which comes from the Greek “seirius”, meaning “burning”, “fiery”). which is located in the constellation Canis Major. Star that rises and sets with the sun from July 22 to August 22, a characteristic period of high temperatures.

Several heat waves have hit France in recent years. There was no heat wave in France during the summer of 2021. The last very extensive and intense episodes took place in 2019, between June 24 and July 7 and July 21 and 27. According to bulletin published by Santé Publique France in September, 1435 deaths were observed (567 during the first heat wave, 868 during the second) including 572 in the departments with red vigilance and 10 workplace victims. The most affected are the over 75s, but the age groups 15-44 and 65-74 were also impacted.

Before, the months of June 2005 and 2006 experienced real heat waves with temperatures often between 35 and 40°Cin particular in the south-east and in the Rhône valley (more than 30°C every day in Lyon in 2006). The biggest heat wave was in August 2003. Its intensity, duration and geographical extent had been exceptional. She had caused 15,000 additional deaths compared to the usual mortality for this time of year. Other memorable heat waves: that of July 1983 “longest observed” remember Meteo Franceand that of the summer of 1947.

The heat wave is associated with very high temperatures day and night for an extended period, usuallyat least 3 consecutive days. On the meteorological level, it is the exceptional nature of the high night temperatures that marks the duration of a heat wave episode. Temperature and duration thresholds are defined and vary according to the departments, explains Meteo France.
For example : in Toulouse, Météo-France speaks of a heat wave when for 3 days and 3 nights we do not go back below 21°C minimum and we exceed 36°C maximum during the day.

The heat wave occurs at different times depending on the country. In France, the period of high temperatures that can lead to a heat wave can start from end of June and continue until August 15.

Each year, the heat wave plan is activated in France on June 1 and until September 15. Its objective is to anticipate the arrival of a heat wave, to define the actions to be implemented at the local and national levels to prevent and limit the health effects and to best adapt the prevention and management measures at the territorial level. paying particular attention to specific populations

The different levels of activation of the heat wave plan are articulated with the 4 colors of meteorological vigilance of Météo France:

1. Level 1 – seasonal monitoring (green vigilance)
2. Level 2 – heat warning (yellow warning)
3. Level 3 – heatwave alert (orange alert)
4. Level 4 – maximum mobilization (red vigilance)

In the middle of a heat wave, simple actions can prevent accidents. It is necessary to prepare BEFORE the first signs of bodily suffering.

• Drink a lot of water without waiting to be thirsty: when it’s hot, your body sweats more than usual and you risk becoming dehydrated. Do not hesitate to always have your bottle of water at hand, to drink up to two liters of water a day! Similarly, avoid diuretic drinks (tea, coffee, soda) as well as alcohol which promotes dehydration.
• Get wet (foggers, wet towels, etc.): to lower body temperature, consider wetting it several times a day, at least the face and forearms. You can also dampen your clothes.
• eat enough and don’t drink alcohol.
• Prefer cool places (to maintain a cool temperature in your home, remember to close the windows and shutters during the day and open them at night. You can also take the opportunity to spend a few hours at the library, cinema, shopping center or museum , as these places are often air-conditioned).
• Limit physical exertion.
• Avoid going out during the hottest hours and spend several hours a day in a cool place.
• Use an air conditioner paying attention to the temperature. It takes no more than 7 degrees difference with the outside temperature to prevent thermal shock when going out. In addition, the colder the temperature, the more frequent headaches or sore throats. Finally, the air blown by the air conditioner should always be aimed at the ceiling, never at you directly.

More than 35°C during the day, no less than 25 at night, and the temperature of the room which does not want to drop… Sleeping well in these conditions is a challenge. Indeed, the body needs to be in a cool environment to access rest, and remains alert when this is not the case: sleep is then lighter, and awakenings more frequent. However, a few simple actions can improve the situation:

Not too many ice cubes in your lemonade, less salt but more sorbets… We explain how to hydrate yourself when the atmosphere becomes suffocating.

The people most at risk in the event of a heat wave are: people over the age of 65 (when you are oldthe body sweats little and has difficulty maintaining itself at 37°C). and infants and children under 4 years of age (the body sweats a lot to maintain the right temperature, the child loses water and risks dehydration). Next come: people with strong physical activity, those working in the heat (bakery, laundry, construction, etc.) and the homeless.

• Heatstroke

Heat stroke or “hypothermia” corresponds to overheating of the body: it can no longer cope with the increase in internal temperature linked to high temperatures. It mainly affects athletes, but also the elderly, outdoor workers and young children during peak heat. This also applies to adults who stay too long in confined and poorly ventilated rooms. For example, staying for hours in a car or in an RER in the heat presents a big risk. The first warning signs that must grow to call 15 without waiting are:

• Muscle cramps in the arms, legs, stomach…
• Unusual aggression, mental confusion, convulsions, loss of consciousness,
• abnormal drowsiness,
• Abnormally hot, red and dry skin,
• Headache, nausea, intense thirst.
• Fever higher than 39°c.

Waiting for help to arrive : transport the person to a cool place, give him something to drink, wet him with cool water, put wet cloths on him, lighten his clothes.

• Dehydration

Puffs of sweat when drinking a glass of water, absence of urine for 5 hours or dark urine, dry lips… Beware of dehydration, which is particularly common in the event of a heat wave. Concretely: a person who sweats and does not drink enough becomes dehydrated. His body lacks water and becomes dehydrated. The elderly are most at risk.

• Hyponatremia

For the elderly, patients with chronic diseases (kidney, heart, liver, respiratory failure, diabetes, cancers, etc.), patients taking certain medications (diuretics, neuroleptics, antidepressants): hyponatremia (decrease in the concentration of salt in the blood) is an increased risk in the event of high temperatures. For those at risk: do not exceed a supply of 1.5 liters of water in addition to foods rich in water, eat a balanced diet, avoid going outside during the hottest hours and see your doctor if you are following a low-salt diet.

• Alcohol and high heat

Consuming alcoholic beverages in hot weather potentially worsens the effects of alcohol and heat on the body.

• An alcoholic drink does not allow you to quench your thirst. On the contrary, alcohol increases the risk of dehydration due to its diuretic action.
• The alcohol does lose more fluid to the body, which more quickly exposes the body to heatstroke.

The best : The prevention of risks related to the interaction between alcohol and high heat requires controlled consumption, the ideal being to drink as little alcohol as possible, if at all. The limit is set at two standard drinks per day for women and three standard drinks per day for men. In case of occasional consumption, it is better not to exceed four standard glasses at once and do not hesitate to drink water between each glass. People with chronic illnesses and pregnant women are advised not to drink alcohol.

• Medicines and heat waves

During a heat wave, the body is weakened. Taking medication carries certain risks under these extreme conditions.

Sources:

Coronavirus SARS-CoV-2: management of the epidemic in the event of the occurrence of heat waves. High Council of Public Health. May 11, 2020

Heat wave and Covid-19: state of knowledge on prevention measures. French Public Health. July 23, 2020