The climate is humid subtropical (Köppen: Cfa), but all around Greater St. Louis has a humid continental climate (Dfa) through the USA isoterm, with a winter that sustains in the coldest month temperatures below 0 °C more easily, clear evidence of an urban heat island, which in the future may cover an even larger area and agglutinate cities and villages to the south.
The climate is humid subtropical (Köppen: Cfa), but Greater St. Louis experiences a humid continental climate (Dfa) through the USA isoterm, with winter temperatures often below 0 °C in the coldest month, indicating an urban heat island that could expand and merge cities and villages to the south.