The current heat wave is very unusual for the second half of August, in the statistics you will not find such a long heat wave with such high temperatures from August 16, with the exception of 1943. Moreover, the nights were and are partly tropical as well. The summer as a whole will go down in history as one of the hottest, but not enough for the top two places.
Exceptionally late heat wave with very high temperatures
Heat waves with at least 3 to 5 days with 30 degrees and more occur from time to time in the first half of August, but in the second half they are the exception. In addition, the maxima reached and still reach values in the range of the absolute maximum values for the second half of August (see table below). In addition, a new all-time record was registered in the night to Monday with a zero degree limit at 5299 m.
| Station | maximum value so far second half of August | absolute maximum second half of August | Rank |
absolute August record |
Start of measurement |
| Zurichberg | 33.4 degrees | 34.3 degrees (19.8. 1943) | 5 | 36.0 degrees | 1881 |
| Bern | 34.9 degrees | 34.0 degrees (19.8. 1943) | 1 | 36.8 degrees | 1864 |
| Basel-Binningen | 34.7 degrees | 37.1 degrees (21.8. 1943) | 10 | 38.6 degrees | 1897 |
| Geneva | 36.7 degrees | 36.2 degrees (20.8. 2003) | 1 | 38.3 degrees | 1864 |
| Sion | 37.0 degrees | 36.4 degrees (20.8. 2012) | 1 | 37.6 degrees | 1958 |
| Chur | 33.8 degrees | 36.2 degrees (19.8. 1972) | 8 | 37.2 degrees | 1959 |
| Samedan | 27.1 degrees | 28.0 degrees (23.8. 1944) | 6 | 28.0 degrees | 1869 |
| Säntis | 17.8 degrees | 20.5 degrees (22.8. 2011) | 10 | 20.5 degrees | 1901 |
| Jungfraujoch | 9.0 degrees | 12.8 degrees (19.8. 2012) | >10 | 12.8 degrees | 1961 |
| Lugano | 33.3 degrees | 33.4 degrees (21.8. 2012) | 2 | 35.9 degrees | 1864 |
It will remain hot until Friday, with the highest temperatures of locally over 35 degrees possible tomorrow Thursday. In Geneva and Sion, 37 degrees and just above are possible, setting new records for the second half of August.
A comparable heat wave in the second half of August occurred only in 1943, when temperatures reached, for example, in Zurich Airport between August 18 and August 21 daily between 33.7 and 34.3 degrees.
Tropical nights
For days now, temperatures have not dropped below 20 degrees (by definition tropical nights), especially at large lakes and at somewhat elevated elevations. Last night, for example, temperatures in Vevey did not drop below 24.7 degrees (see the following hit list). In Lausanne Pully it was with 24.1 degrees the warmest night since the beginning of measurement!
Lowest temperature (as of 08:00)
| Measuring stations | Lowest temperature (in °C) |
|---|---|
| Vevey (383 a.s.l., VD) | 24.7 |
| Lausanne Pully (461 a.s.l., VD) | 24.1 |
| Locarno-Monti (367 a.s.l., TI) | 23.8 |
| Lugano (273 a.s.l., TI) | 23.2 |
| Neuchâtel (485 a.s.l., NE) | 22.8 |
| Le Bouveret (375 a.s.l., VS) | 22.8 |
| Evionnaz (480 a.s.l., VS) | 22.3 |
| Bantiger (942 a.s.l., BE) | 22.1 |
| Gersau (435 a.s.l., SZ) | 21.7 |
| Galgenen (468 a.s.l., SZ) | 21.6 |
| Salvan (990 a.s.l., VS) | 21.4 |
| Uetliberg (869 a.s.l., ZH) | 21.3 |
| Nyon (430 a.s.l., VD) | 21.2 |
| Zurich-Zurichberg (556 a.s.l., ZH) | 21.1 |
| Wädenswil (463 a.s.l., ZH) | 21.1 |
| Cham (440 a.s.l., ZG) | 21.1 |
| Oron-la-ville (830 a.s.l., VD) | 21.0 |
| Schaffhausen (438 a.s.l., SH) | 20.9 |
| Lägern (868 a.s.l., ZH) | 20.9 |
| Stabio (353 a.s.l., TI) | 20.7 |
Until Friday morning there are still partly tropical nights.
Record heat
In Geneva there was yesterday Tuesday already the 12th heat day (maxima over 30 degrees) in a row. In the summer of the century 2003, 13 heat days in a row were recorded here between August 2 and 14, and in July 2022 it was 14. Only in 1983 could a longer series of 16 heat days be recorded.
One of the hottest summers since measurements began
Even though there was a marked drop in temperature at the beginning of August, the summer of 2023 (June to August) in Switzerland will go down in history as one of the warmest. So far, the excess across Switzerland is just under 2 degrees (see Fig. 1). This puts us on track for the third warmest summer since measurements began, after 2003 and 2022.
Fig. 1: Temperature deviation compared to the long-term average 1991 to 2020 in the summer to date; Source: MeteoNews, UBIMET
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