Abstract: Based on the hourly precipitation observation data from 745 regional automatic stations and national stations in western Yunnan and the ERA5 reanalysis data , this paper analyzes the spatial and temporal distribution characteristics of the " 1262 " rainstorms during the flood seasons from 2019 to 2023 and the atmospheric environmental characteristics of 12 h extreme rainstorm processes . The results show that :1) The 2 h rainstorms present a yearly increasing trend , and the annual variation trends of the 6 h and 12 h rainstorms are consistent and fluctuate obviously. The monthly variations of rainstorms are consistent , showing a unimodal pattern , with the most occurrence frequency found in August and the fewest in May. Rainstorms are mainly concentrated in the period from early morning to morning (from 03:00 to 11:00) . More than 57 . 8% of the rainstorms are accompanied by short- time severe precipitation with an intensity of ≥20 mm/h . 2) The frequencies of 2 h , 6 h and 12 h rainstorms are 0 . 3 times/year , 1 . 1 times/year and 1 . 8 times/year , respectively. The rainstorm areas aree mainly located in the western parts of Dehong , Baoshan and Lincang, especially in Xima of Dehong. The rainstorm areas gradually get expanded with the adding duration of rainstorms . The occurrence frequency of 2 h rainstorms in western Yunnan is relatively low. 3) Statistical analysis of the atmospheric environmental characteristics of five extreme 12 h rainstorm processes show that in the extreme rainstorm processes , multiple extremely abnormal dynamic , water vapor , and thermodynamic physical quantities cooperate well with each other. The consistency of abnormally abundant water vapor in different processes is relatively good. The maximum specific humidity at 700 hPa ranges from 12. 5 to 14 . 1 g/kg , and the extreme values of the vertically integrated precipitable water is in the range from 69 . 4 to 90. 1 mm , which is 1 . 9 to 2. 8 times the climate average . In conclusion , these analyzed spatio-temporal distribution characteristics of the " 1262 " rainstorms in western Yunnan and the characteristics of atmospheric environmental parameters during the extreme rainstorm process could provide a reference for improving the refined forecast of " 1262 " rainstorms .