All-season tires are a set of tires that are good for use in most places during most times of the year. All-season tires feature tread patterns and rubber compounds that make them good for use in wet weather and a wide range of hot and cold temperatures that may impact road conditions. The tires are made to stand up to light snow, which means that anyone can use them all year in most temperatures. The rubbers used in all-season tires are designed to stay flexible and pliable, even in temperatures that hover around the freezing mark.
Although they are called all-season, they really are only meant for light snow. If the winter gets especially freezing in Milwaukee, Greenfield, or Madison you may need to look at reliable winter tires for this.