The UTCI (Universal Thermal Climate Index) is the most comprehensive bioclimatic index: it models the human body's thermophysiological response considering air temperature, humidity, wind speed, and radiation (solar and thermal). It classifies thermal stress into 10 categories from "extreme cold stress" (<−40 °C) to "extreme heat stress" (>46 °C).
Advantages
Unlike the heat index (temperature+humidity only) or wind chill (temperature+wind only), UTCI integrates all factors. It is used by the Copernicus Climate Change Service and public health services for heat wave and cold warnings.