Abstract:  In order to forecast heat stroke weather effectively, the heat stroke cases and meteorological conditions were analyzed in Hebei province. The critical index of the daily maximum air temperature which may cause heat stroke was determined, and a formula of hotness index was established based on temperature and humidity. The heat stroke weather grades were divided into four levels by the daily maximum air temperature, hotness index and its duration. According to the effect of heat stroke on human health, some suggestions for different grades were given. Furthermore, the rationality of grade division was tested by meteorological conditions, the heat stroke cases and application of graded index. The results show the forecast index of heat stroke grades is consistent with summer climate distribution characteristics in Hebei province. More than 97% of heat stroke cases occur in the first or second grades of heat stroke. The forecast accuracy rate of grade index reaches 81.2 %. The index has well indicative to forecast heat stroke weather and prevent heat stroke effectively.

Key words: Hotness index, Heat stroke, Meteorological grade, Forecast index