Eleven year (1995—2005) data from 22 observation stations are used in the statistic analysis in order to get the diurnal variation characteristics of convective weather events in Beijing area. The results show that 41.6% thunder s howers, 61.3% hail events and 58.5% gale wind gust events occurred in the period from 1500 BST to 2000 BST. Seven cases in July and August, 2006 are selected to test whether or not the 1400 BST sounding data are useful for the improvement i n forecasting thunderstorms after 1400 BST. Some convection diagnostic parameter s such as CAPE, DCAPE and CIN are calculated based on the sounding data of both 0800 BST and 1400 BST. The results of comparison indicate that 1400 BST sounding data are more helpful than 0800 BST sounding data in forecasting convective wea ther.