Why Frost Laws Exist
When frost leaves the ground in spring, the gravel base beneath Minnesota’s road surfaces becomes saturated with meltwater. The structural capacity of the road drops dramatically — pavement that handles 80,000 lb loads in summer can be damaged by far less weight during the thaw. Minnesota’s frost law system protects road infrastructure by restricting axle weights during this vulnerable period.
The restrictions are not optional, not negotiable, and not something you can risk. Overweight violations during frost law season carry significant fines and can damage roads that cost millions to repair. The state takes enforcement seriously.
How the System Works
Timing
Frost law restrictions typically begin in March and continue through mid-May, varying by year and zone. The thaw progresses from south to north across the state, and restrictions follow the same pattern. Southern Minnesota sees restrictions first; northern Minnesota sees them last.
Key timing rules:
- Restrictions cannot exceed 60 days after placement on any given road
- At least 3 calendar days advance notice before restrictions begin
- Restrictions are lifted when roadbeds stabilize for legal-weight traffic
Restriction Levels
| Level | Axle Weight Limit | Severity | Typical Roads |
|---|---|---|---|
| 5-ton | 10,000 lbs per axle | Most restrictive | Weakest county roads |
| 7-ton | 14,000 lbs per axle | Moderate | Most county roads, some state highways |
| 8-ton | 16,000 lbs per axle | Least restrictive | Stronger state trunk highways |
Which Roads Are Affected
| Road Type | Typically Restricted? | Notes |
|---|---|---|
| Interstates (I-90, I-94, I-35) | No | Generally exempt from frost law restrictions |
| Major US Highways | Usually no | Most remain unrestricted |
| State trunk highways | Some | Check maps — varies by road condition |
| County roads | Yes, widely | Most affected category |
| City streets | Some | Check with local jurisdiction |
The practical impact: your interstate routing is fine. Your last-mile delivery to a shipper or receiver on a county road may not be. A 5-ton restriction means a loaded truck cannot use that road at all.
How to Check Current Status
| Resource | Contact | What It Provides |
|---|---|---|
| MnDOT Load Limits Website | dot.state.mn.us/loadlimits/ | Interactive maps, current restrictions |
| Recorded Information | 651-366-5400 (local) | Current restriction status |
| Toll-Free Hotline | 1-800-723-6543 | Current restriction status |
| MnDOT District Offices | Varies by region | Local road condition detail |
:::tip Bookmark the MnDOT load limits page and call 1-800-723-6543 every morning during thaw season (March through May). Restrictions change as conditions evolve, and what was open yesterday may be restricted today. Make this part of your daily pre-trip routine. :::
Zone Progression
Restrictions roll across Minnesota from south to north as the thaw progresses. A typical season looks roughly like this:
| Zone | Typical Start | Typical End | Duration |
|---|---|---|---|
| Southern Minnesota | Early-mid March | Late April | 6-8 weeks |
| Central Minnesota | Mid-late March | Early-mid May | 6-8 weeks |
| Northern Minnesota | Late March-early April | Mid-late May | 6-8 weeks |
These dates vary annually based on winter severity and spring temperatures. In a warm spring, restrictions may start earlier and end sooner. In a cold spring, everything shifts later.
Planning Strategies
Route to Interstates
The simplest strategy: keep your routing on interstates and major US highways during thaw season. These roads are generally not restricted. If you must use state highways or county roads, check the restriction map before dispatching.
Contact Shippers and Receivers
If your pickup or delivery is on a county road or local route, call ahead. Ask if the access road is restricted. Arriving at a restricted road with a loaded truck creates a problem that no amount of phone calls can solve quickly.
Agricultural Hauling Considerations
Agricultural and bulk commodity haulers are most affected by frost laws because grain elevators, feed lots, and processing facilities are often located on county roads. Spring planting and early-season commodity movement coincide directly with frost law season. Plan loads to stay within restriction limits or route through unrestricted roads.
Comparison With Neighboring States
| State | Frost Law Season | Duration | Key Difference |
|---|---|---|---|
| Minnesota | March through mid-May | 6-8 weeks per zone | Zone-based south-to-north progression |
| North Dakota | March through mid-June | Longest season | Later end date due to northern latitude |
| South Dakota | Feb 15 through April 30 | Earliest start | Earlier start but shorter duration |
| Wisconsin | March through May | Similar to MN | Frozen road program (inverse — heavier loads in winter) |
| Iowa | March through May | Similar to MN | Similar structure |
Insurance and Frost Law Season
Frost laws do not directly affect your Minnesota trucking insurance premiums, but the operational disruption they cause — rerouting, delays, refused loads — affects your bottom line every spring. Proper insurance coverage ensures that if a frost-law-related incident occurs (overweight on a restricted road, road damage liability), you are protected. The combination of frost law season and Minnesota’s no-fault insurance rules makes adequate coverage essential.
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