Abstract: From the evening to the night on April 28, 2019, a weak rainfall occurred in the northern area of Beijing, which had a certain impact on the preparations for the opening ceremony of the Beijing World Horticultural Exposition in China.This article analyzes the causes of the weak-intensity and high-impact rainfall weather and discusses the major concerns of the on-site meteorological service of the major events of the opening ceremony.The results showed that during the opening ceremony of the Expo, it is affected by a weak short-wave trough and the dynamic conditions are relatively weak.Beijing is located at the rear of high pressure and the front of the convergence zone of low pressure, with descending or weak ascending movements at low levels.Various numerical models can forecast the occurrence of this rainfall event, but they do not show obvious advantages in the time and scope of the occurrence of rainfall.Using ground automatic stations, wind profilers, and cloud radars, and other high-resolution detection data, combined with refined model forecast products, it is helpful for forecasters to accurately study the short-term evolution of the precipitation system.Meteorological support for major events often focuses on single-point forecasts.Combining weather-affected risk forecasting services with response plans, and adopting certain service strategies can effectively make up for the shortcomings of forecasts and better bring out the benefits of meteorological services.