Abstract In COST Action 730, a multi-segmental thermophysiological
model was used to describe physiological
strain reactions for different climatic conditions in order to
develop a 'Universal Thermal Climate Index' (UTCI). UTCI
predictions for warm climates were compared with empirical
data from the laboratory tests. The comparison was
performed by means of equivalence lines within a psychrometric
chart so that the combined influence of air
temperature and humidity on physiological strain may be
assessed. Within a reasonable regime of air temperatures
and relative humidities (RH), the differences between
simulated and measured values were as follows: for rectal
temperatures below 0.3°C, for skin temperatures below