Background information

The Apparent Temperature Heatwave Days index is relevant to human health. This Index is part of the Extreme Heat Hazard type of the Heat and Cold category of the classification.

The index gives the number of days with prolonged periods of simultaneous extreme humidity and heat conditions. The apparent temperature is a measure of discomfort due the combination of heat with high humidity based on physiological studies on evaporative skin cooling.

The higher/lower the apparent temperature, the higher/lower the discomfort.


The Apparent Temperature Heatwave Days Index (Number of Days) is defined as a period of at least two consecutive days during the summer months (June, July, August) in which both the daily apparent temperature and the daily minimum temperature exceed their monthly 90th percentiles defined over a reference period. Apparent temperature is a linear function of temperature and dew point temperature to account for humidity conditions.

Data Sources

The data was assembled on behalf of the Copernicus Climate Change Service (C3S) based on climate projections hosted on the C3S Climate Data Store (CDS). The Index data is 30-year period statistics based on a set of four bias-corrected multi-model simulations ensemble from the EURO-CORDEX experiment. These simulations have a spatial resolution of 0.1° x 0.1° and cover scenarios RCP4.5 and RCP8.5. More information about the dataset can be found in the corresponding CDS documentation resources.

Supporting Information

Further information about this application can be found in the Product User Guide (PUG) of the application in the documentation resources of the CDS.

Data download

The aggregated data shown on the map can be downloaded as csv files.

Visualisation and Navigation

The application has an interactive map on the left side with a set of drop down menus to select the regions (NUTS, Transnational regions or Europe Zones), the time span (Year) and the emission scenario (RCP4.5 or RCP8.5). By clicking on the map, a scrolling panel appears on the right side displaying an interactive plot corresponding to spatial and temporal averages over the selected region. Hover over the plot to see the values.

Content in the European Climate Data Explorer pages is delivered by the Copernicus Climate Change Service (C3S) implemented by ECMWF.


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This translation is generated by eTranslation, a machine translation tool provided by the European Commission.