Zone 1: Extends from the Minnesota border, Lake Superior, and the Michigan border south to and including US Highway 8.
Zone 2: Extends from the southern limit of Zone 1 to and including a line defined by US Highway 10, east on State Highway 73, east on State Highway 54, north on State Highway 22/110, east on State Highway 22 east to Lake Michigan east of Oconto (including Highways 10, 22, 54, 73, and 110).
For more information on the frozen roads program including a map of the zones, please visit.
Interested in seeing how WisDOT monitors field conditions to verify frost depths, see the following video:
WisDOT Bureau of Highway Maintenance