The regional weather characteristics in the key and target areas are analyzed to study their effects on air pollution in Tianjin using the NCEP reanalysis data and daily air pollutant observations during the heating season in winters from 2002 to 2005. The results show that high air pollution in heating seasons is associated with climatic characteristics and weather conditions, such as the regional atmospheric circulation and dynamic and thermal characteristics, which affect the diffusion, accumulation, and transportation of air pollutants. Especially, the influence of regional wind velocity on aerial pollutants reflects the contribution of area pollution in North China to air pollution in Tianjin and enhances the transportation convergence of pollutants. The atmosphere diffusion weakens and the pollutants are easy to accumulate while there is wind direction change from north or northwest to west or southwest. The pollution probability increases with the rise of atmosphere instability.