Should be free from snow
While snow is inevitable, it’s also wise (and in some towns a law) to make sure that a driver’s vision, both front and back, are not obstructed.
Wisconsin and Michigan: An object that obstructs the vision of the driver is prohibited. (Snow is an object). Actually the whole vehicle; hood, roof, lights and windows should be free from snow covering.
It’s even unlawful for semi-trailers to have falling snow from the trailer top. It’s always wise to keep yourself safe by clearing the whole vehicle of an obstructed object, even though many laws are not enforced.
Wouldn’t you rather be safe than sorry?