The influence of climate on human body is a synthetic action of many meteorological elements.As usual,air temperature is used to be an index to indicate the warm and cool of environment,but the thermal regulation and thermal comfort of human body can not be assessed only by air temperature or other single meteorological element.The only way to describe the effects of the thermal environment on human body completely is to do by means of a heat balance model.In such model all relevant meteorological parameters,behavioral characteristics(activity and clothing) and body measurements can be considered.By the use of numerical weather forecast results and the model MEMI,the problems of heat balance and ways of solving them are described,and an new thermal indexthe physiological equivalent temperature of human body has been calculated to assess the thermal comfort.