Frost Laws in South Dakota

The Earliest Start in the Northern Plains

South Dakota’s frost law season can begin as early as February 15, making it the earliest start date among northern plains states. The season runs through April 30. While Minnesota’s frost laws typically begin in March and North Dakota’s extend through mid-June, South Dakota’s earlier start reflects its slightly more southern position in the thaw progression.

How the System Works

SDDOT monitors daily high and low temperatures statewide throughout the frost law season. When temperatures and road conditions indicate that roadbeds are vulnerable, restrictions are posted on affected routes.

Key Rules (SDCL 32-22-24)

• Restrictions may be imposed any time after February 15
• Restrictions continue through April 30
• Restrictions are not implemented earlier than necessary
• Restrictions are removed when road conditions stabilize
• At least 48 hours notice before new restrictions take effect

Restriction Levels

SDDOT uses a color-coded Load Limit Restriction Map to display current restrictions. Red indicates the most restrictive (6-ton), yellow indicates moderate (7-ton), and green indicates the least restrictive (8-ton).

Which Roads Are Affected

The same pattern holds across all northern plains states: interstates stay open while county roads and lower-class highways carry restrictions. The last-mile problem is identical to Minnesota’s frost law challenge — your interstate route is clear, but your delivery point may be on a restricted road.

Monitoring Resources

Check the SDDOT load limit restriction map daily during frost law season. Restrictions change as conditions evolve.

Frost Law Season Comparison

South Dakota’s season is shorter than North Dakota’s but starts earlier. Carriers operating across the northern plains need to understand each state’s timing to plan spring operations effectively.

Tire Weight Formula Interaction

South Dakota’s unique tire weight formula (600 lbs per inch of tire width for steering/dual-tired axles, 500 lbs per inch for others) becomes even more significant during frost law season. The per-tire calculation means your actual allowed weight per axle may be lower than the posted restriction level if your tires are narrow. Calculate your actual limits before loading during frost law season.

Planning Strategies

For Agricultural Haulers

Grain elevators, feed operations, and processing facilities in South Dakota sit on county roads that are the first to be restricted. Spring planting logistics overlap directly with frost law season. Plan loads to fit within restriction limits, route through unrestricted roads when possible, and coordinate with shippers on access road status.

For I-90 Through-Traffic

I-90 corridor traffic is generally unaffected by frost laws, as the interstate remains unrestricted. The concern is for loads requiring pickup or delivery off the interstate during frost law season.

For LCV Operations

South Dakota’s 129,000 lb LCV allowance is suspended on restricted roads during frost law season. LCV operators must reduce loads to within posted restrictions on affected routes.

Insurance Considerations

Frost law season creates operational pressure that can lead to violations, rerouting through unfamiliar roads, and delayed loads. South Dakota trucking insurance should provide coverage that accounts for the seasonal disruption and the increased risk of incidents when carriers adjust their operations around weight restrictions.