Boston Harbor

ANZ230 · Coastal Waters Forecast, National Weather Service Boston/Norton MA · issued Sat, Sep 26, 4:03 AM EDT

Storm Warning in force. Today: NE winds 20 to 25 kt, increasing to 25 to 30 kt this afternoon. Gusts up to 50 kt. Waves 2 to 3 ft, except 5 to 7 ft at the outer harbor entrance. Patchy fog. Showers. A chance of tstms this afternoon. Vsby 1 to 3 NM, decreasing to 1 NM or less this afternoon.

Boston Harbor on the map

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Storm Warning
Gale Warning

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Now

The nearest stations reporting each, as of Sat, Sep 26, 5:00 AM EDT.

Wind: NE 20 kt, gusts 24 kt at CSIM3
Water: 61°F at 44013

Alerts in force

Storm Warning from Sat, Sep 26, 1:58 AM EDT until Sat, Sep 26, 8:00 PM EDT

Storm Warning issued September 26 at 1:58AM EDT until September 26 at 8:00PM EDT by NWS Boston/Norton MA

The full text

* WHAT...Northeast winds 20 to 25 kt with gusts up to 50 kt and
waves 2 to 4 feet.

* WHERE...In Massachusetts coastal waters, Boston Harbor. In
Rhode Island coastal waters, Narragansett Bay.

* WHEN...Until 8 PM EDT this evening.

* IMPACTS...Storm force winds and hazardous waves will capsize
or damage vessels and reduce visibility.

Mariners should remain in port, alter course, and/or secure the
vessel for severe conditions.

The forecast

Coastal Waters Forecast from National Weather Service Boston/Norton MA, issued Sat, Sep 26, 4:03 AM EDT, valid until Sat, Sep 26, 5:00 PM EDT. Wind in knots, seas in feet.

STORM WARNING IN EFFECT THROUGH THIS EVENING

Today: NE winds 20 to 25 kt, increasing to 25 to 30 kt this afternoon. Gusts up to 50 kt. Waves 2 to 3 ft, except 5 to 7 ft at the outer harbor entrance. Patchy fog. Showers. A chance of tstms this afternoon. Vsby 1 to 3 NM, decreasing to 1 NM or less this afternoon.
Tonight: NE winds 25 to 30 kt with gusts up to 50 kt. Waves 2 to 3 ft, except 5 to 7 ft at the outer harbor entrance. Patchy fog. Showers. Vsby 1 NM or less, increasing to 1 to 3 NM after midnight.
Sunday: NE winds 20 to 25 kt with gusts up to 45 kt. Waves 2 to 3 ft, except 5 to 7 ft at the outer harbor entrance. Patchy fog. Showers. Vsby 1 to 3 NM.
Sunday night: NE winds 15 to 20 kt with gusts up to 35 kt. Waves 2 to 3 ft, except 4 to 6 ft at the outer harbor entrance. Showers. Patchy fog in the evening with vsby 1 to 3 NM.
Monday: NE winds 15 to 20 kt with gusts up to 25 kt. Waves 2 to 3 ft, except 4 to 6 ft at the outer harbor entrance. Showers.
Monday night: NE winds 10 to 15 kt with gusts up to 20 kt, diminishing to 5 to 10 kt after midnight. Waves 2 to 3 ft in the evening, then 1 foot or less. At the outer harbor entrance, waves 2 to 4 ft. Showers.
Tuesday through Wednesday night: SW winds 5 to 10 kt. Waves 1 foot or less, except 2 to 4 ft at the outer harbor entrance.

Winds and waves higher in and near tstms.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

Synopsis

Synopsis for Massachusetts and Rhode Island coastal waters

A slow moving and intensifying nor'easter approaches southern New England this evening and lingers over the southern waters into this weekend. Dangerous conditions are expected for mariners today through this weekend. Peak NE wind gusts of 35 to 60 kt with maximum seas of 15-25 feet across the open waters are expected. Mariners should keep up to date with the latest forecasts and be prepared to return to port.

Buoys and stations nearby

The latest report from each station within reach of the zone, nearest first. Distances in nautical miles from the middle of the zone.

Station	Distance	Wind	Water	Air	Pressure	Reported
CSIM3 Castle Island (NOS) 8444069	3 nm	NE 20 kt, gusts 24		58°F		Sat, Sep 26, 4:48 AM EDT
44013 BOSTON 16 NM East of Boston, MA	13 nm	NE 27 kt, gusts 35	61°F	60°F	1012.9 hPa	Sat, Sep 26, 5:00 AM EDT
44029 Buoy A01 - Massachusetts Bay	20 nm	ENE 19 kt, gusts 23		59°F		Sat, Sep 26, 4:30 AM EDT
FOXR1 8454000 - Providence, RI	38 nm	NNE 15 kt, gusts 21	62°F	58°F	1009.4 hPa	Sat, Sep 26, 4:48 AM EDT
PVDR1 8453662 - Providence Visibility, RI	39 nm	NNE 12 kt, gusts 21		58°F	1011.6 hPa	Sat, Sep 26, 4:48 AM EDT
FRVM3 8447386 - Fall River, MA	40 nm		65°F	57°F	1010.9 hPa	Sat, Sep 26, 4:48 AM EDT

The past year

Warnings, watches and advisories the National Weather Service issued for this zone over the past 12 months, from the Iowa Environmental Mesonet’s archive.

Product	Issued	Most recent
Gale Warning	30	Fri, Sep 25, 2026, 8:00 AM EDT
Special Marine Warning	5	Wed, Jul 22, 2026, 4:27 PM EDT
Storm Warning	5	Fri, Sep 25, 2026, 2:00 PM EDT
Gale Watch	16	Thu, Jun 18, 2026, 11:00 AM EDT
Storm Watch	1	Mon, Mar 16, 2026, 5:00 PM EDT
Small Craft Advisory	65	Tue, Sep 22, 2026, 6:35 AM EDT
Freezing Spray Advisory	2	Sat, Feb 7, 2026, 4:00 PM EST

What this means

Marine forecasts give wind in knots (1 knot is 1.15 mph) and seas in feet, except the high seas forecasts, which give seas in meters. Seas are the significant wave height, the average of the highest third of the waves; individual waves may be more than twice that. On the Great Lakes the forecast gives waves, not seas. "Wave Detail" splits the seas into the wind waves and each swell, with its direction and period.

Each coastal office writes a Coastal Waters Forecast for the bays, sounds and ocean out to 20 to 60 nautical miles, or on the Great Lakes a Nearshore Marine Forecast within 5 nautical miles of shore; the Open Lakes Forecast covers the rest of each lake. The Ocean Prediction Center and the National Hurricane Center write the Offshore Waters Forecasts out to about 250 nautical miles, and the High Seas Forecasts beyond. Forecasts are issued at least twice a day and updated when they go wrong.

Small Craft Advisory: Winds or conditions hazardous to small boats. The thresholds are set by each NWS region: typically sustained winds or frequent gusts of 20 to 25 knots up to 33 knots, and seas of 5 to 7 feet or more.
Gale Warning: Sustained winds or frequent gusts of 34 to 47 knots, not from a tropical cyclone.
Storm Warning: Sustained winds or frequent gusts of 48 to 63 knots, not from a tropical cyclone.
Hurricane Force Wind Warning: Sustained winds or frequent gusts of 64 knots or more, not from a tropical cyclone.
Special Marine Warning: A thunderstorm or squall over the water with winds or gusts of 34 knots or more, hail of 3/4 inch or more, or a waterspout, for up to two hours.
Hazardous Seas Warning: Wave heights or steepness at or above the office’s warning threshold, when the wind alone does not warrant a warning.
Heavy Freezing Spray Warning: Spray freezing on a vessel at 2 cm (3/4 inch) an hour or more.
Tropical Storm and Hurricane Warnings: Tropical storm (34 to 63 knots) or hurricane (64 knots or more) conditions expected within 36 hours. Watches: possible within 48 hours.

Nearby

Open the live map with marine zones and buoys The hour-by-hour forecast for the middle of the zone Suffolk Area Beaches Eastern Norfolk Area Beaches Eastern Essex Area Beaches Every Atlantic Coast zone

Sources

Coastal Waters Forecast CWFBOX from National Weather Service Boston/Norton MA, issued Sat, Sep 26, 4:03 AM EDT. Original at NWS. Buoy reports from the National Data Buoy Center. Past products from the Iowa Environmental Mesonet. Zone outlines from the NWS marine and offshore zone boundaries. Warnings and advisories from the NWS API, read 09:32 UTC. All public domain, from the National Weather Service.