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From Town Tools. For the current version, visit https://www.towntools.org/boston-massachusetts-us/harbor-high-tides
The highest predicted high tides ahead for Boston Harbor — the dates the water runs highest, when the low-lying waterfront is most exposed. These are astronomical tide predictions, not a flood forecast: on a calm day the tide alone stops just short of flood stage, and it takes an onshore wind, heavy rain or a coastal storm piling on top to push water onto the streets.
Next big tide
11.2 ft, Mon, Oct 26 at 11:37 AM
Tides to watch
Date
High tide
Predicted height
Mon, Oct 26
11:37 AM
11.2 ft
Tue, Oct 27
12:21 PM
11.5 ft
Wed, Oct 28
1:08 PM
11.6 ft
king tide
Thu, Oct 29
1:58 PM
11.5 ft
Fri, Oct 30
2:52 PM
11.2 ft
Tue, Nov 24
10:09 AM
11.5 ft
Against the flood line
The highest predicted tide ahead, 11.6 ft, comes 0.7 ft below NOAA's minor coastal-flood stage (12.3 ft). On a calm day the tide alone stops short of the line — it is wind, rain and storm surge piling on top that push water over it.
Where the water goes
Long Wharf & the downtown waterfront
The harborwalk and the lowest stretches of Long Wharf take on water on the highest tides; a modest wind or storm surge on top is what reaches the pavement. (Boston Globe, 2025.)
Morrissey Boulevard, Dorchester
Morrissey Blvd floods several times a year on high tides driven up by wind and rain, closing lanes along the shore. (Boston Globe, 2025.)
East Boston waterfront (Central Square / East Pier area)
Low-lying blocks near the East Boston shoreline are among the first to see water back up through drains on a king tide with surge behind it. (Boston Globe, 2025.)
The Seaport & Fort Point Channel
Built on filled tidal flats and ringed by the channel, the Seaport's lowest streets and the Fort Point harborwalk flood when a high tide meets wind or heavy rain. (Boston Globe, 2025.)
How to read this
These are official astronomical tide predictions, in ft above MLLW. They tell you how high the water would rise on the tide alone, on a calm day.
Whether water actually reaches the street depends on wind, rain and storm surge on top of the tide. This is not a flood forecast. For warnings, follow the channel below.
Official warnings
National Weather Service — Boston / Norton (BOX), and the City of Boston
Coastal-flood watches, advisories and warnings come from the NWS — issued when wind, rain or storm surge are expected to push water above the predicted tide. For street closures and emergency notices, follow the City of Boston (Office of Emergency Management) and call 311 for non-emergencies, 911 in an emergency.
Predictions are from NOAA's Boston station on the downtown waterfront, in the inner harbor — the harbor itself, not any one street. Heights are in feet above the average low-tide line (MLLW).
Predictions: NOAA CO-OPS (Center for Operational Oceanographic Products and Services) tidesandcurrents.noaa.gov. Station: Boston — Station tide tables. as of October 12 at 7:49 AM.