The unusually hot period for the second half of August will end tomorrow, Friday, and the weather situation will change fundamentally. Downpours and partly heavy thunderstorms accompany the beginning drop in temperature, in the course of the weekend a forming genoa low will also play an important role.
More thunderstorms during the night and Friday morning
After the partly strong thunderstorms that have unloaded on Thursday evening (we have reported in detail further down in this blog), the night to Friday and Friday morning was also thundery in the very north of Switzerland. In addition, a few new info.
Number of lightnings whole Switzerland until 08:00: 35'000
Canton with the most lightnings: Thurgau
The area most affected by thunderstorms was from the northern Jura to Lake Constance. In these regions, the largest amounts of rain were also recorded. Locally, the thunderstorms brought up to more than 40 mm of rain.
Fig. 1: Rainfall amount for the last 24 hours; Source: MeteoNews AG / UBIMET
Precipitation amount (as of 08:10)
| Measuring stations | Precipitation amount (in mm) |
|---|---|
| Montsevelier (JU) | 45 |
| Delémont (JU) | 42 |
| Basel-Binningen (BL) | 37 |
| Mervelier (JU) | 36 |
| Amriswil (TG) | 36 |
| Bärschwil (SO) | 36 |
The high pressure, which has been dominating the weather lately, is now weakening more and more. Today, there are more, especially in the late afternoon and evening partly also again strong thunderstorms. With today, the striking heat wave also comes to an end!
Violent thunderstorms with gale-force winds!
As expected, early Thursday evening brought showers and thunderstorms first in the Jura and the Alps, later also in the lowlands. These thunderstorms had it partly in itself! In addition to heavy precipitation with intensities of up to or partly even more than 100 mm/h, they also brought gale-force winds, even hurricane-force gusts were present!
Initially, northwestern Switzerland and the Alps were most affected - in the evening, heavy thunderstorms repeatedly formed or intensified over the Jura and moved further to the northeast. Some time later, however, a line of thunderstorms also moved across the central midlands to eastern Switzerland, so that intense precipitation, squalls and locally hail could also be registered here.
Fig. 1: Precipitation on Thursday, August 24, 2023 at 19:35. Heavy thunderstorms moved over northwestern Switzerland and the Mittelland, among others; Source: MeteoNews
Gale-force winds were also measured in the lowlands, one on St. Chrischona, one in Schaffhausen. Gale-force gusts were measured in Delsberg, Bischofszell, Altenrhein and in St. Gallen, among other places. In other regions of Switzerland, the thunderstorms produced squalls (= wind peaks of 75 to 102 km/h).
Strongest wind gusts (<1000m, as of 21:30)
| Lowland stations | Strongest wind gusts (in km/h) |
|---|---|
| St. Chrischona | 129 |
| Schaffhausen | 128 |
| Delémont | 116 |
| Bischofszell | 113 |
| Altenrhein | 109 |
| Uetliberg | 109 |
| Sankt Gallen | 108 |
| Härkingen | 108 |
| Basel-Binningen | 100 |
| Beznau | 93 |
| Zurich-Zurichberg | 92 |
| Einsiedeln | 90 |
| Cressier | 90 |
| Zurich-Reckenholz | 89 |
| Würenlingen | 88 |
| Glarus | 86 |
| Egolzwil | 83 |
| Leibstadt | 83 |
| Wädenswil | 82 |
| Neuchâtel | 80 |
The intense precipitation was accompanied in part by quite a bit of rain. In Delémont, 38.8 mm were recorded, with 18.5 mm falling within 10 minutes and 10.7 mm later within the same time. But also in Basel-Binningen it partly poured like from buckets, within 10 min 13.8 mm were measured here.
Fig. 2: Precipitation total from 24 August 2023 to 9 pm. Northwestern Switzerland and regions along the Alps and Pre-Alps were most affected.; Source: UBIMET, MeteoNews
Until 21:40 o'clock about 28'000 lightnings were registered all over Switzerland, a proud sum. The biggest light show was in Thurgau with about 5000 flashes and in St. Gallen with about 4400 flashes.
Fig. 3: Registered number of flashes from August 24, 2023 to 21:40; Source: UBIMET, MeteoNews
In the next few hours, the weather will calm down, but the risk of showers and thunderstorms will remain somewhat elevated. Tomorrow Friday morning, the risk of showers increases further, especially in the direction of the Jura and the Alps. The weather tomorrow and over the weekend is described in detail in this blog below.
Highest temperature of the year and several records!
Thursday afternoon brought the expected peak of this heat wave, the expectations were even slightly exceeded! The rising southwesterly wind pushed the temperature in Geneva to 39.3 degrees. This is a new August record at this station, the second highest value of the measurement series and also the second highest value on the north side of the Alps since the beginning of measurement! The absolute maximum value is 39.7 degrees in Geneva and comes from July 7, 2015. In addition, there were new all-time records in Nyon, Payerne, Mathod and Crans Montana. Sion equaled its all-time record of August 13, 2003 with 37.6 degrees.
Fig. 1: Maximum temperatures on August 24, 2023; Source: MeteoNews, Ubimet
Highest temperature (as of 17:00)
| Measuring stations | Highest temperature (in °C) |
|---|---|
| Geneva (420 a.s.l.) | 39.3 |
| Nyon (430 a.s.l.) | 38.5 |
| Payerne (490 a.s.l.) | 38.2 |
| Mathod (435 a.s.l.) | 38.2 |
| Sion (482 a.s.l.) | 37.6 |
| Glion (774 a.s.l.) | 37.0 |
| Fribourg-Posieux (646 a.s.l.) | 36.5 |
| Visp (640 a.s.l.) | 36.5 |
| Basel-Binningen (316 a.s.l.) | 36.4 |
| Delémont (439 a.s.l.) | 36.3 |
| Beznau (325 a.s.l.) | 36.3 |
| Evionnaz (480 a.s.l.) | 36.2 |
| Würenlingen (334 a.s.l.) | 36.1 |
| Bern-Belpmoos (510 a.s.l.) | 36.0 |
| Koppigen (484 a.s.l.) | 36.0 |
| Leibstadt (341 a.s.l.) | 36.0 |
| Mosen (453 a.s.l.) | 35.9 |
| Schaffhausen (438 a.s.l.) | 35.8 |
| Gösgen (380 a.s.l.) | 35.7 |
| Buchs-Aarau (387 a.s.l.) | 35.7 |
Tonight and in the first half of the night, partly heavy thunderstorms are on the agenda. With our precipitation radar you can keep an overview.
Very hot, but also increasing tendency to thunderstorms
Today, Thursday, the late heat wave swings to a peak once again, potentially reaching the highest temperatures of the entire phase today. Widespread 33 to 35 degrees, in the Geneva area and in the Rhone Valley it is 37 to 38 degrees. The highest value of the year so far in Switzerland is 37.6 degrees on July 11 in Chur, this mark is definitely within reach today. Geneva in particular, with a little southwesterly wind, is a hot candidate in the truest sense of the word! The sun dominates, but some Sahara dust clouds the view. In the afternoon, more and more clouds will form over the mountains, which will lead to the first downpours and thunderstorms. In the lowlands, it is very likely to be dry until the evening, but during the night, partly heavy thunderstorms are possible.
Fig. 1: Calculated maximum temperatures on August 24, 2023 (ECMWF); Source: MeteoNews, Ubimet
Probably the last widespread heat day of the year.
Tomorrow, Friday, we will be in the area of a southwesterly flow, on this path we will continue to receive very warm, but also humid air. After overnight thunderstorms, local downpours are already possible again, especially in the Jura and on the northern edge, and by noon the tendency for showers will also increase along the foothills of the Alps. This development will continue in the afternoon, starting from the Jura and the Alps, new thunderstorm cells will increasingly form, which may later also reach the lowlands. Temperatures will once again reach highs around or just above 30 degrees, it will be oppressively humid. The zero degree line lies between 4300 and 4500 meters. The thunderstorms, some of them strong, will continue well into Saturday night.
Thundery interspersed downpours
Saturday will be unsettled and already noticeably less warm. This is not so much due to the air mass itself, but mainly to the cloudiness –. After a long time, the sun will once again have some serious competition. Interrupted by dry phases, rain showers pass through again and again, and it can still thunder and lightning. When it rains, it pours! Temperatures in the north reach a muggy 23 to 24 degrees, in the south it is still up to 28 degrees.
Fig. 2: Outlook for the coming days; Source: MeteoNews
Especially in the east and south a lot of rain
On Sunday, we will be in the area of an air mass boundary. Sunday morning will be rainy practically all over the country, but in the afternoon the rain will ease in the west. In the south and east, however, it continues to rain – and often heavily. In the south, there are also embedded thunderstorms. The sun will be absent most of the time, temperatures will vary only in the range of 20 degrees. Over the Gulf of Exactly a low pressure system begins to form, thus the air mass boundary remains almost stationary over the Alpine region. Also on Monday, there will be heavy and thundery rain in the south. How much central and eastern Switzerland are still affected by this, the models are not yet completely agreed. In any case, in total there will be considerable amounts of precipitation!
Fig. 3: 48-hour precipitation totals through Monday, August 28 06 a.m. UTC ; Source: MeteoNews, Ubimet
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