46 CFR 42.30-5: Northern winter seasonal zones and area

Last reviewed: October 14, 2026

This section describes the boundaries of the North Atlantic Winter Seasonal Zones I and II, the North Atlantic Winter Seasonal Area, and the North Pacific Winter Seasonal Zone. It gives the winter and summer seasonal periods for each. In the North Atlantic Winter Seasonal Area, the periods depend on vessel length.

What it says

  1. North Atlantic Winter Seasonal Zone I has a winter period from October 16 to April 15 and a summer period from April 16 to October 15.

    46 CFR 42.30-5(a)(1)(i)“Winter: October 16 to April 15. Summer: April 16 to October 15.”

  2. North Atlantic Winter Seasonal Zone II excludes North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by the parallel of the latitude of The Skaw in the Skagerrak.

    46 CFR 42.30-5(a)(2)“Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by the parallel of the latitude of The Skaw in the Skagerrak.”

  3. North Atlantic Winter Seasonal Zone II has a winter period from November 1 to March 31 and a summer period from April 1 to October 31.

    46 CFR 42.30-5(a)(2)(i)“Winter: November 1 to March 31. Summer: April 1 to October 31.”

  4. In the North Atlantic Winter Seasonal Area, vessels over 328 feet in length have a winter period from December 16 to February 15 and a summer period from February 16 to December 15.

    46 CFR 42.30-5(b)(1)(i)(a)“Winter: December 16 to February 15. Summer: February 16 to December 15.”

  5. In the North Atlantic Winter Seasonal Area, vessels of 328 feet and under in length have a winter period from November 1 to March 31 and a summer period from April 1 to October 31.

    46 CFR 42.30-5(b)(1)(i)(b)“For vessels of 328 feet and under in length:”

  6. The North Pacific Winter Seasonal Zone has a winter period from October 16 to April 15 and a summer period from April 16 to October 15.

    46 CFR 42.30-5(c)(1)“(1) Seasonal periods: Winter: October 16 to April 15. Summer: April 16 to October 15.”

Common questions

What are the winter dates for North Atlantic Winter Seasonal Zone I?

The winter period is October 16 to April 15. The summer period is April 16 to October 15.

“Winter: October 16 to April 15. Summer: April 16 to October 15.”

Do the seasonal dates in the North Atlantic Winter Seasonal Area depend on vessel length?

Yes. Vessels over 328 feet in length have a winter period from December 16 to February 15, while vessels of 328 feet and under in length have a winter period from November 1 to March 31.

“For vessels of 328 feet and under in length:”

What does North Atlantic Winter Seasonal Zone II exclude?

It excludes North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by the parallel of the latitude of The Skaw in the Skagerrak.

“Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by the parallel of the latitude of The Skaw in the Skagerrak.”

The text of 46 CFR 42.30-5

Electronic Code of Federal Regulations (eCFR), current as of March 31, 2026 · Read it on eCFR

Northern Winter Seasonal Zones and area

(a) North Atlantic Winter Seasonal Zones I and II. (1) The North Atlantic Winter Seasonal Zone I lies within the meridian of longitude 50° W. from the coast of Greenland to latitude 45° N.; thence the parallel of latitude 45° N. to longitude 15° W.; thence the meridian of longitude 15° W. to latitude 60° N.; thence the parallel of latitude 60° N. to the Greenwich Meridian, thence this meridian northwards.

(i) Seasonal periods:

Winter: October 16 to April 15. Summer: April 16 to October 15.

(2) The North Atlantic Winter Seasonal Zone II lies within the meridian of longitude 68°30′ W. from the coast of the United States to latitude 40° N.; thence the rhumb line to the point latitude 36° N., longitude 73° W.; thence the parallel of latitude 36° N. to longitude 25° W.; and thence the rhumb line to Cape Torinana. Excluded from this zone are the North Atlantic Winter Seasonal Zone I and the Baltic Sea bounded by the parallel of the latitude of The Skaw in the Skagerrak.

(i) Seasonal periods:

Winter: November 1 to March 31. Summer: April 1 to October 31.

(b) North Atlantic Winter Seasonal Area. (1) The boundary of the North Atlantic Winter Seasonal Area is the meridian of longitude 68°30′ W. from the coast of the United States to latitude 40° N.; thence the rhumb line to the southernmost intersection of the meridian of longitude 61° W. with the coast of Canada; and thence the east coasts of Canada and the United States.

(i) Seasonal periods:

(a) For vessels over 328 feet in length:

Winter: December 16 to February 15. Summer: February 16 to December 15.

(b) For vessels of 328 feet and under in length:

Winter: November 1 to March 31. Summer: April 1 to October 31.

(c) North Pacific Winter Seasonal Zone. The southern boundary of the North Pacific Winter Seasonal Zone is the parallel of latitude 50° N. from the east coast of the Union of Soviet Socialist Republics, to the west coast of Sakhalin; thence the west coast of Sakhalin to the southern extremity of Cape Kril'on: thence the rhumb line to Wakkanai, Hokkaido, Japan; thence the east and south coasts of Hokkaido to longitude 145° E., thence the meridian of longitude 145° E. to latitude 35° N., thence the parallel of latitude 35° N. to longitude 150° W. and thence the rhumb line to the southern extremity of Dall Island, Alaska.

(1) Seasonal periods:

Winter: October 16 to April 15. Summer: April 16 to October 15.

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of March 31, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.