New Hampshire Frost Laws & Spring Thaw Limits
New Hampshire posts state highways at 30,000 lb gross during spring thaw, or total tire width in inches times 300, whichever is less, set each year by NHDOT district engineers (RSA 236:3-a). Towns post local roads on their own timing under RSA 231:191. The posted sign is your hard limit. Heating-oil, milk, maple-sap, and septic trucks can be exempted with approval. The Interstate is not posted. Check NHDOT and New England 511 before you load.
How New Hampshire handles spring thaw
New Hampshire posts state highways at 30,000 lb gross during spring thaw, or total tire width in inches times 300, whichever is less, set each year by NHDOT district engineers (RSA 236:3-a). Towns post local roads on their own timing under RSA 231:191. The posted sign is your hard limit. Heating-oil, milk, maple-sap, and septic trucks can be exempted with approval. The Interstate is not posted. Check NHDOT and New England 511 before you load.
Window, reduction, and where to check
- Season: Spring thaw, roughly late February or March through April or May, set each year by NHDOT district engineers as frost leaves the road base. Municipalities post local roads on their own timing.
- Reduction: A posted weight cap. On posted state highways the limit is 30,000 lb gross, or the total tire width in inches times 300, whichever is less. Towns post local roads separately. The roadside sign is the hard limit.
- Interstates: Exempt from the seasonal reduction
- Find the current order: Check NHDOT 'Weight Restrictions - Spring Postings' and the New England 511 site (newengland511.org) under Trucking, New Hampshire, Seasonal Posting. Towns post their own roads, so confirm local ways with the town before you run them.
- Overweight penalty: Standard New Hampshire overweight penalty applies to a posted violation; confirm the current fine with NHDOT. Home-heating-oil, processed-milk, maple-sap, and septic-pumper trucks can be exempted from the seasonal limit with district engineer approval (RSA 236:3-a).
New Hampshire Frost Law FAQ
Does New Hampshire have frost laws?
When are New Hampshire's spring weight restrictions in effect?
How much do the limits drop in New Hampshire?
Do New Hampshire's frost laws apply to the Interstates?
Reference information for planning, not legal advice. Traffic laws change and this can be out of date, so always confirm the current statute and obey posted signs before you rely on it. Last reviewed July 2026. Source: https://www.dot.nh.gov/services/weight-restrictions-spring-postings. See our Terms & Disclaimer.
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