Picture this: your haul is scheduled, your route approved, and your OSOW permits in hand — until a local “Seasonal Weight Restriction” notice suddenly invalidates your route overnight.

Every winter, states and provinces enforce Seasonal Weight Limits to protect thaw-softened roads from heavy damage. But for truckers and dispatchers, these temporary laws can cause costly delays, permit reapplications, and route detours if you’re not prepared.

Here’s everything you need to know about how seasonal weight limits work, why they exist, and how to avoid fines or downtime during the frost season.

What Are Seasonal Weight Limits?

Seasonal Weight Limits (SWLs) — also called Frost Laws — are temporary restrictions placed on certain roads, usually in late winter and early spring, when pavement strength is at its weakest.

When frost in the ground begins to thaw, water saturates the soil, reducing its ability to bear heavy loads. To prevent structural damage, transportation agencies temporarily lower the legal axle weight limits on affected roads.

• Typical reduction: 10–35% less weight per axle.

• Duration: usually 4–8 weeks, depending on weather and soil temperature.

• Enforcement: local and state police, DOT inspectors, and weigh stations.

Why These Restrictions Matter for Heavy Haul Operators

For most vehicles, weight limits mean a simple slowdown.
For heavy haul and oversize carriers, it’s a logistical challenge:

• Approved OSOW routes may suddenly close.

• You may need special spring permits or bonded detours.

• Insurance and compliance liabilities increase if your load exceeds new temporary limits.

When and Where Do Seasonal Weight Limits Apply?

Each region enforces SWLs differently.
Here’s a quick overview of how U.S. states typically handle it:

Minnesota Feb–Apr Up to 10 tons per axle Divided into five frost zones
Michigan Feb–May25–35% “Frost Law” enforced on secondary roads
North Dakota Mar–Apr20% Load restrictions depend on sub-grade depth
Wisconsin Mar–Apr15–25% Seasonal Weight Permits may be issued
Montana Variable Up to 30% Based on pavement moisture readings
Canada (AB, SK, MB) Feb–May Up to 40% Governed by spring thaw bulletins

(Always check DOT updates — start and end dates vary yearly.)

How Seasonal Weight Limits Affect OSOW Permits

1. Temporary Suspension of Existing Permits

Some states automatically invalidate or suspend OSOW permits on restricted roads until conditions improve.

2. Route Rerouting Required

Permitted carriers must detour to designated frost-resistant highways. These routes may increase distance — and cost.

3. Special Spring Permits

Certain jurisdictions (like Wisconsin and Michigan) issue Seasonal Weight Permits that authorize limited operation during thaw periods under specific conditions.

4. Escort and Timing Adjustments

Escort requirements and travel hours often change during thaw season to reduce road stress and congestion.

How to Stay Compliant During Frost Season

1. Check DOT Bulletins Weekly

• Subscribe to your state’s Frost Law updates.

• Use interactive DOT maps showing active restrictions.

• Plan multi-state hauls using up-to-date SWL notices.

2. Adjust Your Load Schedule

If you regularly transport heavy equipment, schedule your largest loads before thaw periods.
Psychology cue (Control): planning ahead gives you leverage when others are scrambling for re-permits.

3. Work With a Permit Service (Like OSOWPermits)

Our team monitors SWL changes in real-time and reroutes your OSOW applications to ensure you stay compliant — even when states change rules mid-week.

4. Educate Drivers and Dispatchers

Quick team training goes a long way:

• Recognize SWL signs and colors.

• Understand weight tables by axle type.

• Know when to contact dispatch before proceeding on restricted roads.

The Financial Cost of Ignoring Seasonal Restrictions

ViolationPotential CostOverweight on restricted road$1,000–$10,000 fineRoute non-complianceImmediate permit revocationRoad damage liabilityFull repair cost billedVehicle impoundmentUp to 7 days + storage fees

It’s not just about avoiding fines — it’s about protecting your operating authority and reputation.