Heat poses a serious danger to people, animals, the environment and infrastructure. High temperatures can have an adverse effect on human health. Recent scientific studies on heat-related mortality show that heat stress is affected by both maximum daytime temperatures and temperatures during the night. In addition, both long as well as short and intense periods of heat impact human health.
Heat warnings are only issued for categories 2, 3 and 4, since heatwaves more extreme than this are very unlikely to occur at these latitudes.
| Possible impacts | Severe risk of circulatory problems |
|---|---|
| Description of meaured and forecasted values | Daily mean temperature ≥ 27 °C for at least three consecutive days. |
| Possible impacts | Significant risk of circulatory problems |
| Description of meaured and forecasted values | Daily mean temperature ≥ 25 °C for at least three consecutive days. |
| Possible impacts | Significant risk of circulatory problems |
| Description of meaured and forecasted values | Daily mean temperature ≥ 25 °C for at least three consecutive days. |
Despite summerlike temperatures, widespread effects on human health or the healthcare system are not yet expected. Nevertheless, fragile individuals may begin to feel unwell at these temperatures and must therefore protect themselves accordingly.
See What to do if a period of heat is forecast or the website of the Federal Office of Public Health (FOPH, in German, French and Italian)
MeteoSwiss issues heat warnings based on the daily mean temperature (Tmean). Tmean is a meteorologically robust index as it does not depend on individual temperature peaks but takes into account the temperature development over the course of the entire day (24 hours). It is calculated as the average of all temperature measurements during one day (from midnight to the following midnight). Using Tmean as heat indicator also allows MeteoSwiss to take into account the night time temperatures. The temperature during the night is particularly important for the human organism. If the nights are too warm, the human body is not able to cool down sufficiently and to recover from daytime heat stress. Our organism can therefore cope less with the heat.
The thresholds and criteria used in the new heat warning system are based on scientific analyses done by the Swiss Tropical and Public Health Institute (Swiss TPH Basel), customized for Switzerland. The study takes into account the effects of mean daily temperature on mortality. According to their study, even one day with high temperatures already leads to an increase in mortality. Taking this into account, from summer 2021, MeteoSwiss has introduced a level 2 warning in the new heat warning concept to warn against short, intense heat periods.
The MeteoSwiss heat warning concept is based on the daily mean temperature and does not take into account other meteorological parameters. In addition to temperature, humidity also has an influence on human well-being, but not on mortality, according to various studies in the Swiss climate.
The MeteoSwiss heat warning concept is based on the daily mean temperature and does not take into account other meteorological parameters. In addition to temperature, humidity also has an influence on human well-being, but not on mortality, according to various studies in the Swiss climate.