Our perception of heat is affected by the following meteorological parameters: air temperature, radiation from the sun, relative air humidity, and wind.
- Heat = the perceived discomfort as a result of excessive air temperature
- Heatwave = a period of extreme heat stress, which can endanger human health
Since heat is better tolerated at low relative air humidity, the heat warnings from MeteoSwiss are based on a calculated value that combines temperature and relative humidity: the so-called heat index.
In Switzerland, heatwaves usually occur in conjunction with high-pressure conditions and a south to south-westerly flow of air, so that warm, dry air is pushed toward the Alpine region.