Universal Thermal Climate Index

The aggregated monthly average and standard deviation index

Here the available via the API climatic variables are presented and described. The detailed reference for the API can be found here.

Index Definition

The universal thermal climate index (UTCI) is a human biometeorology parameter that is used to assess the linkages between outdoor environment and human well‐being. Thermal comfort indices describe how the human body experiences atmospheric conditions, specifically air temperature, humidity, wind and radiation [1].

Calculation Parameters

The universal thermal climate index (UTCI) is an equivalent temperature (°C), it is a measure of the human physiological response to the thermal environment. The UTCI describes the synergistic heat exchanges between the thermal environment and the human body, namely its energy budget, physiology and clothing. UTCI takes into consideration the clothing adaptation of the population in response to actual environmental temperature [1]. There are four variables required to calculate the UTCI:

  • Air temperature at 2 meters

  • Dew point temperature at 2 meters

  • Wind speed at 10m above ground level

  • Mean radiant temperature

Source Dataset

The dataset used is from Copernicus Climate Service [2]. It provides a complete historical reconstruction for a set of indices representing human thermal stress and discomfort in outdoor conditions. This dataset, also known as ERA5-HEAT (Human thErmAl comforT) represents the current state-of-the-art for bioclimatology data record production.

The dataset is organised around two main variables:

  • the mean radiant temperature (MRT)

  • the universal thermal climate index (UTCI)

These variables describe how the human body experiences atmospheric conditions, specifically air temperature, humidity, ventilation and radiation.

The dataset is computed using the ERA5 reanalysis from the European Centre for Medium-Range Forecasts (ECMWF). ERA5 combines model data with observations from across the world to provide a globally complete and consistent description of the Earth’s climate and its evolution in recent decades. ERA5 is regarded as a good proxy for observed atmospheric conditions.

The dataset currently covers 01/01/1940 to near real time and is regularly extended as ERA5 data become available.

The dataset is produced by the European Centre for Medium-range Weather Forecasts.





Universal thermal climate index


For any combination of air temperature, wind, radiation and humidity, the Universal thermal climate index is defined as the air temperature of a reference outdoor environment that would elicit in the human body the same physiological model’s response (sweat production, shivering, skin wettedness, skin blood flow and rectal, mean skin and face temperatures) as the actual environment.


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