The All Season tire classification is a compromise between one developed for use on dry and wet roads during summer and one developed for use under winter conditions. The type of rubber and the tread pattern best suited for use under summer conditions cannot for technical reasons, give good performance on snow and ice
All-Season tires are also marked for mud and snow the same as winter tires but rarely with a snowflake. Owing to the compromise with performance during summer, winter performance is usually poorer than a winter tire.
Mud and Snow, (or M+S, or M&S), is a designation applied rather arbitrarily by manufacturers for all-season and winter tires designed to provide improved performance under low temperature conditions, compared to summer tires
Dedicated winter tires will bear the "Mountain/Snowflake Pictograph" if designated as a winter/snow tire
A "snowflake on a mountain" symbol means that the tire has exceeded the industry requirement for a reference (non-snow) tire