As at the beginning of each month, we offer you a climatological report of the past month. Place therefore in the mapped balance sheet of the month ofAUGUST 2023 in terms of temperature, rainfall and sunshine on a panel of 73 stations*. The statistics are calculated under the official climate average for the period 1991-2020.
“Contrast” is the perfect term to sum up this month of August, despite a new positive thermal anomaly (+0.9°C nationwide) and this for the 19th consecutive month (a memory).
Car this month had started in a certain freshness and even a first somewhat autumnal taste on certain days (anomaly of -2.1°C from August 1 to 9). The very end of the month also had below average (-1.7°C from August 26 to 31). But these two cool sequences did not make it possible to compensate for the remarkable warm period that lasted from August 10 to 25 (+3.6°C), punctuated by a exceptional heatwave and never seen past August 15.
It is therefore this heat wave at the end of August 2023 that will remain in the climatological annals, mainly from August 20 to 24, when many absolute records (whether for minimum or maximum temperatures) were beaten in particular by Occitanie and the Auvergne-Rhône-Alpes region. The day of August 24 has also become the hottest ever observed in France post-August 15 (indicator of 27.76°C). Sometimes more than 30°C at the “least hot” of the night, and maximum temperatures above 43 or even 44°C, such was the finding of this heat wave, the full report of which is to be found >>.
Daily temperature anomaly in August 2023 in France – deviation from the 1991-2020 mean – Infoclimat
If this month of August was therefore ultimately above average (indicator of 22.0°C), we are well below the month of August observed last year (23.7°C), and especially much cooler than the historic and unbeatable month of August 2003 (24.9°C). As for the coolest months of August, we have to go back overall before the 1980s, with a minimum observed in August 1963 (indicator of 17.9°C, ie 4.1°C less than this year).
Average of the national thermal indicator in August since 1946 – Infoclimat
If we note a chronological contrast with an alternation of cool and warm sequences, the contrast is also very present geographically speaking. For indeed, this heat wave did not affect the northern half of France, which remained subject to conditions simply in line with the averages north of the Loire (no global anomaly in Paris or Rennes, a very slight deficit of -0.2°C in Le Touquet and -0.3°C in Lorient). On the entire Météo-France network, the most marked negative anomaly amounts to -0.8°C near Chevillon (Haute-Marne).
Of the noticeably more summery conditions going towards the southern regions or the east of the country, more permanently confronted with this heat wave. From Midi-Toulousain to Auvergne and the Lyon region, the thermal anomaly exceeds sometimes +2°C (up to +2.2°C in Toulouse and +2.4°C in Puy-en-Velay). Locally, the anomaly even reaches the +3°C on the secondary network (+3.8°C in Saint-Agrève in Ardèche, and +3.2°C in Cessy in Ain).
On the rainfall side, the national balance on our panel of stations is perfectly balanced and therefore within the average. But here too, this balance actually hides a new North-South contrast.
After just average temperatures, theRegions north of the Loire harvested much higher rainfall than usualin particular following a turbulent first decade, and a particularly active front on August 31 between the Manche and Hauts-de-France: we note then surpluses of +69% in Beauvais, +75% in Le Touquet, +97% in Nancy and even more than double the average total in Metz (+114%). Other areas wetter than usual: lextreme south-east of the country and the south of the Alps, due to a short rainy-stormy sequence on August 26 and 27 having ended the heat wave. Usually dry, this month of August therefore ended with anomalies of up to +40% in Nice, +85% in Marseille-Marignane, +104% in Ajaccio… and even +286% in Calvi and +315% in Levens (Alpes-Maritimes), i.e. 3 times the usual August average (a very low average, hence the remarkable surpluses).
For the rest, it was a month in deficit over a large southern half (with the exception of the extreme south-east and south of the Alps, but also the Pyrenean foothills), with deficits sometimes ranging between -50% et -70% in Languedoc-Roussillon (-69% in Nîmes), in certain parts of Aquitaine (-72% in Mont-de-Marsan), the Massif-Central (-55% in Aurillac) or even in the south of Centre-Val-de-Loire region (-51% in Bourges).
A contrast which is reflected at the level of accumulations by values often included between 60 and 100mm north of the Loireor even 100 to 130mm locally between the Grand-Est, Hauts-de-France and Normandy (127mm in Metz, 128mm in Le Touquet and 133mm in Nancy). The national maximum on the secondary network is to the credit of the station of Ballon-de-Servance (Haute-Saône) with 215.5mm. Pyrenees also well watered with 211mm near Cauterets (Hautes-Pyrénées).
Some regions of the southern half have not been served as much in terms of rain, with accumulations sometimes lower than 20mm in Occitania (12mm in Montpellier and Perpignan), in the Charentes (17mm in Cognac) or le littoral Provençal (9mm in Hyères). And despite large surpluses, the Côte d’Azur and Corsica did not harvest a lot of water with 32mm in Ajaccio or 24mm in Nice.
Months of contrasts on the temperature side, on the rain side… but also on the sunshine side! If the anomaly on a national scale is only slightly marked on our panel of stations (sunshine deficit of -6%), it again hides a very large disparity between the North and the South of France.
A northern half where we can therefore really speak of a gloomy month given the particularly poor sunshine during the month of August (often between -10 et -20%). A generalized deficit, and an abnormally gray and cloudy over the Centre-Val-de-Loire where the balance even drops locally to -30% (-28% in Chartres and -30% in Orléans).
To find a more consistent sunshine, or even theslightly excessyou had to be on the southernmost cities. Occitanie, Sud-Aquitaine, Provence, Côte d’Azur and Corsica therefore ended this month with slight excess sunshine of around +5 to +10% approximately, even going up to +12% on the side of Mont-de-Marsan.
Such deficits on the northern half resulted in sunshine often much less than 200 hours. On the Centre-Val-de-Loire, northern Brittany or the English Channelthe sun only appeared between 150 and 170h in total during this month (160h in Orléans, 159h in Cherbourg, 158h in Chartres). The national minimum is also Breton with 148 hours for Brest.
On the southern half, if the 200 hours are greatly exceeded, the total even easily exceeds 300 hours around the Mediterranean, more than double the amount of sunshine observed in several northern cities. The maximums are also for the cities of Nîmes (336h), Bastia (342h), Ajaccio (348h), Marseille-Marignane (349h), and even 358h at Luke (Var, not present on our panel).
Summary:
* PANEL OF 73 STATIONS
Temperature – rainfall – sunshine:
Agen, Ajaccio, Albi, Alençon, Angers, Aurillac, Bastia, Beauvais, Bergerac, Besançon, Biarritz, Bordeaux, Bourg-Saint-Maurice, Bourges, Brest, Brive, Caen, Carcassonne, Charleville-Mézières, Chartres, Châteauroux, Cherbourg, Clermont-Ferrand, Cognac, Colmar, Dijon, Embrun, La-Roche-sur-Yon, Langres, Le Mans, Le-Puy-en-Velay, Le Touquet, Limoges, Lorient, Luxeuil, Lyon-Bron, Mâcon, Marseille- Marignane, Melun, Millau, Mont-de-Marsan, Montélimar, Montpellier, Nancy-Essey, Nantes, Nevers, Nice, Nîmes-Courbessac, Niort, Orléans, Paris-Montsouris, Perpignan, Poitiers, Rennes, Saint-Brieuc, Saint- Etienne, Saint-Dizier, Saint-Auban, Saint-Geoirs (Grenoble), Saint-Girons, Strasbourg, Rouen, Tarbes, Toulouse-Blagnac, Tours, Troyes.
Temperature – rainfall (partial or total absence of sunshine data):
Abbeville, Lille, Metz, Hyères, Romorantin, Saint-Quentin.
#Weather #news #Weather #climate #report #August #contrasting #remarkable #heat #wave
