The invention discloses a medium-range forecast 
system and method for cold, rainy and snowy weather based on atmospheric variable physical 
decomposition. By utilizing the atmospheric space three-dimensional multivariable and time continuous grid data outputted in the past observed, the current observed and the medium-range 
numerical weather prediction modes, and the physical 
decomposition of the climate and the weather disturbance quantity, a 
causality between the regional sustained low temperature, rain and 
snow and freezing 
extreme weather events and the weather disturbance prior to and during the events is established in the method. According to the invention, a physical 
decomposition of the climate seasonal variation field and the day-to-day weather disturbance field is carried out according to the data of day-to-day three-dimensional space grid point temperature, altitude and wind and the like of the 
atmosphere from the 
troposphere to the 
stratosphere in the 
northern hemisphere for nearly 30 years, and a 
database for the atmospheric climate field and the weather disturbance field can be established; and a historical 
database of the low temperature, rain and 
snow and freezing weather in 
south China is established according to the data of day-to-day temperature and 
precipitation from the national meteorological 
station for nearly 50 years. The invention provides not only an inquiring 
system for historical low temperature, rain and 
snow and freezing weather events, but also a forecasting 
system for medium-range low temperature, rain and snow and freezing weather events.