normalsperiode

Normalsperiode, or climate normals, is a statistical concept used in climatology to define typical weather conditions for a location over a fixed time span. It represents the long-term average values of weather variables such as temperature, precipitation, and sunshine, and serves as a baseline against which current observations are compared. By comparing recent weather to the normals, analysts can determine whether conditions are unusually hot, cold, wet, or dry for that location and time of year.

A normalsperiode lasts 30 consecutive years. The specific variables included can vary by country, but temperature, precipitation, and humidity are commonly used. Values are typically computed as simple averages across all years in the period, and deviations of current observations from these averages are expressed as anomalies. This framework makes it possible to assess departures from normal conditions over time.

Historically, many regions used 1961–1990 as the standard normals period. In recent decades, 1991–2020 has been adopted as the contemporary standard by many meteorological services, with updates planned every 30 years under guidance from the World Meteorological Organization. As climate change progresses, normals are periodically revised to reflect new baselines, while still enabling comparisons with past records.

Normals are not weather forecasts; they describe typical conditions and variability over a long run. They support planning in sectors such as agriculture, energy, infrastructure, and tourism by providing a consistent reference frame for interpreting current weather. See also climate normals, climatology, meteorology.