Critical values of meteorological factors were identified for improvement of ecological and public health prognosis of the concentration of pollen grains in the air that increase the risk of allergy in the human population. Risk of allergy symptoms from Ambrosia, Artemisia, or Poaceae pollen arise when the pollen grain concentration in the air increases over threshold values. In this study, an integrated indicator -the "weather factor" WF, was developed. It was based on measurements of air temperature, relative humidity, and atmospheric pressure. The results of the study can be used to assess the prognosis of the appearance of potentially dangerous concentrations of pollen grains in the atmosphere to predict the occurrence of pollinosis in the population of the central region of Ukraine, based upon weather factors.