Southern Illinois
Southern Illinois happens being on the border between humid continental climate (Köppen climate classification Dfa) and humid subtropical climate (Köppen climate classification Cfa). The area doesn't have any large mountains or large bodies of water to moderate its temperature. That means Southern Illinois areas are prone to both cold Arctic air and hot, humid tropical air from the Gulf of Mexico. Along with the rest of the Midwestern United States, such areas are home to some of the largest temperature extremes in the world. The Southern Illinois area has four distinct seasons. Spring is the wettest season. It has uneven severe weather. This involves severe thunderstorms, tornadoes or winter storms. Summers are hot and humid. This season only has occasional and brief rest. Humidity often makes the heat index rise to temperatures feeling well above . Fall is mild with lower humidity. It can, however, make irregular bouts of heavy rainfall with the first snow flurries. This usually happens during late November. Winters are cold with periodic snow. During this season, temperatures often below freezing. Thaws are usually frequent. Winter storm systems, in particular the Alberta clippers and Panhandle hooks, often bring days of heavy freezing rain, ice pellets and snowfall.