Abstract: The relation between weather processes in early and mid-summer is investigate d using the NCAR/NCEP daily 500 hPa reanalysis data. It is shown that if there is a anomalously strong increase process of 500 hPa height over North China in June , then there will be more days when the circulation pattern of “west high east lo w" dominates over North China in July and August, and the rainfall will be less; conversely, if there is a quite deep low process over North China in June, then there will be more days when the circulation pattern of “west low east high " do minates in July and August, and the rainfall will be more. Correlation coefficie nts of the daily maximum positive height anomaly over the North China High regio n (40°-45°N, 100°-115°E) in June with the day number of the circulation patt ern of “west high east low" in July and August over North China, and the mid-sum mer rainfall in North China are 0.597 and 0.562 , respectively. Based on the a bove analysis results, a short rang climate forecast empirical method for mid-summer rainfall in Tianjin was established, and its performance in the operational forecasts for mid-summer rainfall in Tianjin in 2002-2004 is quite well.