Abstract: Adequate water vapor and cloud phase changes are two necessary conditions for rainfall to occur. Based on the BeiDou-3 satellite navigation system, water vapor can be retrieved, which has the advantages of high time resolution and accuracy; FY-4A can provide cloud phase parameters with a resolution of 15 minutes. This article uses the BDS-3 and FY-4A data to analyze the spatiotemporal changes in atmospheric precipitation and cloud phase before and after the occurrence of all precipitation in August 2022. Through comparison, three characteristics of extreme rainfall in Datong “817” were obtained: firstly, the perceptible water vapor increased one hour before rainfall, reaching a rate of 3.17 mm/h, significantly exceeding the general rainfall level of the same period; before the second rainfall, there were multiple changes in cloud types between multi-layer clouds and opaque ice clouds, and eventually extreme rainfall occurred in the form of opaque ice clouds; the third reason is that the height of extreme rainfall cloud tops is usually greater than 10000 meters.