A mean annual rain and snow precipitation of 31 inches is one of the chief climatic factors that make the State a uniformly humid region with a constant water supply for all but the smallest of streams. The heaviest rains fall in the spring and summer months. As well as plentiful rain, there is plentiful sun; half of Wisconsin's days are shiny.
Wisconsin's position between 42° 30' and 47° north latitude places it in the belt of prevailing westerly winds and within the temperate zone. Weather changes are numerous and rapid and there is a marked difference between summer and winter. Lakes Superior and Michigan have only a very limited influence in checking the temperature extremes of the very cold winters, like those of northern Sweden and central Russia, or of the hot summers, comparable to those of France, Germany, and southeastern England. Fifty degrees below zero to 111 degrees above are the recorded limits of Wisconsin temperatures. Within these extremes, temperatures vary according to the altitude of a given region, according to the northern or southern position of that region, and according to the proximity of lake bodies. Thus the growing seasons range between a shortest season of 75 days for a small part of Wisconsin that borders Michigan and a longest season of 175 days for the southwestern corner of the State.
Among Wisconsin's greatest natural assets are its soils, many of them immensely rich deposits of the glaciers. The latter, including tills or unsorted clays and sands, assorted gravels and sands, and red clays of glacial lake beds, cover the larger part of the State. Other Wisconsin soils are divided between residual -- products of weathering of underlying rocks -- and those transported by the wind. The residual and wind-blown soils include a sandy soil, the results of the weathering of sandstone, and a clay soil mixture composed of weathered limestone and a wind-brought silt called loess.