Michigan Frost Laws & Spring Thaw Limits

How Michigan handles spring thaw

Michigan is the textbook frost-law state. On MDOT-designated Seasonal routes your weight drops 25% on concrete and 35% on asphalt, often with a 35 mph cap (MCL 257.722). All-Season routes hold full legal weight. The window runs roughly mid-February to mid-May by frost zone and moves every year. County and city roads post their own 'X ton' signs. Pull MDOT's current bulletin before you load.

Window, reduction, and where to check

• Season: Declared by MDOT frost zone each spring as the thaw moves north. March, April, and May are the statutory reduced-loading months, but MDOT can start earlier in a hard year; in 2026 restrictions ran from February 17 and the last lifted May 15. Dates shift every year, so pull the current bulletin.
• Reduction: On MDOT-designated 'Seasonal' routes the cut is 25% on rigid (concrete) pavement and 35% on flexible (asphalt) pavement, often with a 35 mph speed cap. 'All-Season' routes hold full legal weight. County and city roads post their own limits.
• Interstates: Exempt from the seasonal reduction
• Find the current order: MDOT Spring Weight Restriction bulletins and the Truck Operators Map at mdotjboss.state.mi.us, or the MDOT restriction hotline 800-787-8960. Counties and cities post their own seasonal signs, so check the local road authority for the roads at each end.
• Overweight penalty: Standard Michigan overweight schedule, charged per pound over: about 3 cents per pound once you're 1,000-2,000 lb over, climbing to 20 cents per pound past 10,000 over (MCL 257.724). A seasonal overload is treated as any overweight violation, and you'll shed or redistribute before rolling.

More for Michigan