Varmedagsantal

Varmedagsantal, meaning “warm day count,” is a metric used in meteorology and climate science to quantify the number of days in a specified period when the temperature exceeds a defined warm‑day threshold. It is typically calculated from daily temperature observations and can be based on daily maximum temperature (Tmax) or daily mean temperature (Tmean).

Computation and variations: A period such as a month, season, or year is selected, and each day that meets the threshold is counted. Common thresholds are 25°C for a warm day and 30°C for a hot day, but thresholds may be relative to local climatology or set by the study. Some definitions use Tmax, others use Tmean, and in multi-site analyses the result may be averaged across stations or reported for each site.

Interpretation and use: Varmedagsantal provides a simple summary of how often conditions exceed a chosen warmth level, useful for climate impact assessments, heat exposure analysis, urban planning, and energy demand forecasting. It is relatively easy to compute and interpret but is sensitive to the chosen threshold and to data quality and coverage. Different definitions can lead to different results, so consistency is important when comparing regions or time periods.

Limitations: The measure does not reflect the intensity or duration of warmth beyond the count of days, and it may mask variations within days or across locales. Missing data handling and station coverage can also influence the outcome.

See also: heatwave metrics, growing degree days, temperature thresholds.