Heat wave confirmed next week – The Weather Channel

By Regis CREPET, meteorologist
Posted on 05/03/22, updated on 05/05/22 at 10:48 The first heat wave of the year in France is expected next week and could be quite long. 25°C will be exceeded on the northern half, and the 30°C mark will be reached in the south. In some ways, it will be quite exceptional for the season. You announce a heat wave from next Monday. Why speak of a heat wave rather than a heat stroke or heat spike? Régis Crépet: A heat wave is a prolonged episode of abnormally high temperatures generally higher by 3 to 5°C compared to the monthly average temperature. This duration must be greater than three days and must also be geographically extended, which will be the case next week, where we will be up to 8°C above these averages in places. If the hot anomaly is more pronounced and continues during the nights, then we speak of a heat wave. On the other hand, if the episode is short or more localized, we speak of heat stroke. The arrival of the #heat is confirmed for next week 🌡️ It will be moderate heat north of the Loire, but more marked and quite durable south of the Loire. Temperatures would be 3° to 5°C higher than average during the week 🥵 pic.twitter.com/zptb9uvkNO — La Chaîne Météo (@lachainemeteo) May 3, 2022 What are the regions concerned and the expected temperatures? RC: From Monday, the temperatures will settle between 22 and 25°C in the north of the Loire, and 25 to 30°C in the south where the first 30°C of the year will be reached. The hottest days are expected to be Thursday and Friday, but the heat could extend beyond that for the southern half. The feeling will be very different from what we experienced during this spring. With the air of subtropical origin, this heat will be almost heavy, with warm evenings conducive to barbecues and late dinners on the terrace. This feeling could be close to 29°C in Paris and 35°C in the southwest, where the wind will be light. Is it an intense and early heat wave for the season? RC: No. Last year it had been hot earlier. The first 25°C (which corresponds to the heat threshold) had been reached at the end of March in Paris, whereas this year, that has not yet happened. In addition, in France, the month of May is characterized by the appearance of the first heat waves of the season. So there is nothing surprising. The months of May 2011, 2017 and 2020 had been particularly hot, with temperatures reaching 30°C in Paris and 35°C in the south. We will not reach these values ​​next week, but this will contrast sharply with this spring which has not seen widespread hot days. Note however that without being exceptional, with a duration of at least 7 days, this heat wave is quite durable. In Paris, the record for the number of days over 25°C dates back to May 1998 with 14 days. It had been 10 days in May 2020. Sometimes at 48 hours forecasts are difficult. At that time, isn’t there a risk that the situation will change completely? RC: The reliability regarding the global change in weather pattern is good. While the North Sea anticyclone has dominated so far with a northeasterly flow, the Azores anticyclone will move up over France early next week, bringing warm subtropical air. Good warm weather is guaranteed south of the Loire, however the uncertainties concern the Channel coasts where clouds could circulate. We estimate at 60% the probability of reaching 25°C north of the Loire and at 90% in the Landes. As summer approaches, the drought is already making headlines with a significant deficit in many regions. Is the future situation worrying? RC: The dryness of surface soils has already been very present in our territory since the end of winter, with rainfall deficits reaching 60% north of the Seine, in the plains of the center-east, and up to 80% in PACA. As long as the temperatures remained moderate, the evaporation of the vegetation remained moderate, but with the arrival of heat, evapotranspiration will be accentuated and the soils will dry all the more quickly, which will quickly aggravate the situation. We can therefore reasonably be concerned about this situation when the summer has not even started. Does this mean that the summer will be scorching? RC: No. A heat wave in May does not mean a hot summer, the climate and atmosphere are not so disciplined! If we look at the statistics, we see that dry and hot months of May are rather followed by summers with the same characteristics at around 60%. But if we take 2011, 2017 and 2020, three recent years with very hot May months, we see that the summer of 2011 was simply standard, the summer of 2017 quite hot and dry, and the summer of 2020 particularly hot. . Nevertheless, we can try to answer the question of the typology of the coming summer with our seasonal forecasts. In mid-April, they saw a summer that was drier and hotter than the average in France, but without noticeable excess. We will see if this trend is confirmed during the update on April 10th.