Heat peak: this week, time, what to do?

[Mise à jour le 17 mai 2022 à 10h51] The heat which has been installed since the beginning of the month continues this week. The mercury will start to rise again, reaching, in the middle of the week, 30 to 34°C in most regions, informed Meteo France. “This is an exceptional heat episode due to its earliness, its sustainability and geographic scope, specify the site. Many heat records for a month of May could be exceeded in the north and the southwest. Some cities like Lyons might know at least 5 days immediately exceeding the high heat threshold (30°C), a extremely rare event in May, observed only once in a century of data (May 16–20, 1945). On the other hand, “a heat episode in May does not make it possible to make forecasts for the summer” emphasizes Meteo France. What is a heat spike? What difference with the heat wave ? At what timeare the temperatures at their maximum during the day?

France experiences heat peaks every summer, sometimes until September, with temperatures that can exceed the 40 degrees in some cities. the biggest heat record in France was recorded in Vérargues in the Hérault on June 28, 2019 with a temperature of 46 degrees. The previous record dated August 12, 2003 in Conqueyrac (44.1°c).

A “heat peak” characterizes a brief episode, usually 24 to 48 hours, during which temperatures are well above normal for the season. It can occur locally on a meteorological station but also over an extended territory. We are completely in this case for the current episode. This intense heat presents a risk for human health, for fragile or overexposed populations, in particular due to their working conditions and physical activity; it can be associated with the yellow weather vigilance level.

A heat wave is an episode of high temperatures, day and night, over an extended period. To identify them, temperature and duration thresholds are defined and vary according to the departments. For example, in Toulouse, Météo-France will speak of a heat wave when for 3 days and 3 nights we do not go back below 21°C mini and that we exceed 36°C max during the day. Heat wave vigilance is based on these thresholds but also takes into account multiple public health criteria linked to the local environment, such as the vulnerability of populations, for example. A extreme heat wave :and exceptional in terms of its duration, its intensity, its geographical extent, with a strong health impact, with the appearance of collateral effects; it is associated with the level of red meteorological vigilance.

During the summer, the legal time in France is shifted by approximately 2 hours (in addition) compared to that of the sun (1 hour in winter). The solar radiation received is at its peak around 2 p.m.hour legal. As explained by Météo France, the ground permanently loses energy by emitting infrared radiation and by exchange with the layers of air near the ground. During the day, the ground heats up as long as the energy it receives from the Sun is greater than that lost by the emission of infrared radiation. The temperatures climb until 4-5 p.m. where they reach a peak then the solar radiation decreases, the ground cools, the temperatures begin to decline until the early morning.

During the heat wavethe hottest times to avoid for going outside or ventilating homes are included between 11 a.m. and 9 p.m. The the coolest hours are between 5 a.m. and 9 a.m.

Variation in temperature at Parc Montsouris (Paris) during the 2003 heat wave.

• Take warm showers or baths regularly during the day, without drying yourself completely, for example.
• Stay inside your home in the coolest rooms and at best, in a cooled space (set your cooling system 5°C below the ambient temperature).
• In the absence of cooling, spend at least 2 or 3 hours a day in a cool place: department stores, cinemas, public places.
• Avoid going outside during the hottest hours (11 a.m. – 5 p.m.).
• Prefer early morning or late evening, stay in the shade as much as possible, do not settle in direct sunlight.
• Wear a hat, light (cotton) and loose clothing, preferably light-coloured.
• Avoid outdoor activities requiring excessive energy expenditure (sports, gardening, DIY, etc.).
• Have a fogger with you when you leave your house and bathe to prevent your body temperature from rising.

The heat has an impact very quickly. The state of health of the most fragile people can deteriorate rapidly and require urgent care.

• Help dependent people (infants and children, elderly people, people with disabilities, people with mental disorders) in theirr regularly offering drinks, even when they don’t ask for them.
• Regularly call your neighbors and/or elderly and/or disabled relatives to check in on them regularly.

Source : Air temperature, educational sheetMeteo France.