Hitzetage

Hitzetage is a meteorological term used in German-language climate reporting to refer to calendar days on which the maximum temperature reaches a high threshold. In Germany, the standard definition applied by the Deutscher Wetterdienst (DWD) is a day with a daily maximum temperature of 30°C (86°F) or higher at a given location. The exact threshold can vary by country or region, with some datasets using somewhat lower or higher criteria depending on local climate norms. Hitzetage are counted for each calendar day and are used to quantify heat exposure during the warm season.

Measurements are based on official daily observations from meteorological stations with standardized siting and exposure. The tally of Hitzetage typically occurs in summer months but can occur in late spring or early autumn during unusually warm periods.

Across Europe and Central Europe, the frequency of Hitzetage has risen in recent decades as part of broader warming trends. Higher counts correlate with heat stress risks, power demand, and urban heat island effects, especially in cities where the built environment intensifies heat exposure. Public health and weather agencies use Hitzetagen in heat warnings and risk communication, as well as in climate impact assessments.

Understanding Hitzetage supports planning for infrastructure, cooling measures, and emergency response. The concept is related to but distinct from heat waves (Hitzewellen), which refer to multi-day episodes of extreme heat rather than individual days.