Abstract: Seasonal variability regarding the nature of precipitation and the activity of cumulus convection during the 1991 Meiyu season of Changjiang-Huaihe River Basin (Jianghuai) has been investigated by calculating apparent heat source/apparent moisture sink and analyzing TBB data. It is found that three periods of strong ascending motion during the Meiyu season lead to three episodes of heavy rain, and the latent heat due to precipitation is of the sole heat source of the atmosphere over Jianghuai during the three rain episodes. The nature of precipitation shows distinct seasonal variability, from frontal precipitation of the first episode to the extremely strong convective precipitation of the third episode. The spatial and temporal distributions of Q1 and Q2 which describe the strong vertical eddy heat and moisture transport during the mid-late stage of the Meiyu are presented in detail.