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Web Portal Changes: The Advanced Hydrologic Prediction Service (AHPS) hosted at will be replaced by the National Water Prediction Service (NWPS), with a target of March 2024. Existing AHPS content and features will be preserved and expanded within NWPS.

Experimental National Water Center Products: Flood Inundation Mapping services are now available for 10% of the U.S. population. Please visit for more information. The National Hydrologic Discussion, Area Hydrologic Discussion, Flood Hazard Outlook, and real-time geospatial services depicting River Forecast Center and National Water Model forecasts, continue to be accessible via the URL above, as described in the StoryMap here.

Hydrograph River at a Glance Download
Boston Harbor at Boston (IN MLLW) Tide Height (ft)Observed: -0.17 ft at 6:00PM Sep 30, 2023Observed: -0.12 ft at 6:54AM Oct 01, 2023Observed: 12.04 ft at 1:00PM Oct 01, 2023Highest Observation: 12.15 ft at 1:12PM Oct 01, 2023Observed: 12.13 ft at 1:18PM Oct 01, 2023Observed: 12.08 ft at 1:30PM Oct 01, 2023Observed: 12.03 ft at 1:36PM Oct 01, 2023Observed: 11.94 ft at 1:42PM Oct 01, 2023Observed: 11.86 ft at 1:48PM Oct 01, 2023Observed: 11.75 ft at 1:54PM Oct 01, 2023Observed: 11.65 ft at 2:00PM Oct 01, 2023Observed: 11.52 ft at 2:06PM Oct 01, 2023Observed: 10.07 ft at 2:54PM Oct 01, 2023Observed: 9.84 ft at 3:00PM Oct 01, 2023Observed: 9.59 ft at 3:06PM Oct 01, 2023Observed: 9.35 ft at 3:12PM Oct 01, 2023Observed: 9.11 ft at 3:18PM Oct 01, 2023Observed: 8.86 ft at 3:24PM Oct 01, 2023Observed: 8.61 ft at 3:30PM Oct 01, 2023Observed: 8.36 ft at 3:36PM Oct 01, 2023Observed: 8.15 ft at 3:42PM Oct 01, 2023Observed: 7.9 ft at 3:48PM Oct 01, 2023Observed: 7.62 ft at 3:54PM Oct 01, 2023Observed: 7.34 ft at 4:00PM Oct 01, 2023Observed: 7.07 ft at 4:06PM Oct 01, 2023Observed: 6.81 ft at 4:12PM Oct 01, 2023Observed: 6.52 ft at 4:18PM Oct 01, 2023Observed: 6.25 ft at 4:24PM Oct 01, 2023Observed: 5.96 ft at 4:30PM Oct 01, 2023Observed: 5.65 ft at 4:36PM Oct 01, 2023Observed: 5.32 ft at 4:42PM Oct 01, 2023Observed: 5.04 ft at 4:48PM Oct 01, 2023Observed: 4.69 ft at 4:54PM Oct 01, 2023Observed: 4.39 ft at 5:00PM Oct 01, 2023Observed: 4.1 ft at 5:06PM Oct 01, 2023Observed: 3.81 ft at 5:12PM Oct 01, 2023Observed: 3.49 ft at 5:18PM Oct 01, 2023Observed: 3.18 ft at 5:24PM Oct 01, 2023Observed: 2.9 ft at 5:30PM Oct 01, 2023Observed: 2.58 ft at 5:36PM Oct 01, 2023Observed: 1.57 ft at 6:00PM Oct 01, 2023Observed: 1.31 ft at 6:06PM Oct 01, 2023Observed: 1.1 ft at 6:12PM Oct 01, 2023Observed: 0.88 ft at 6:18PM Oct 01, 2023Observed: 0.68 ft at 6:24PM Oct 01, 2023Observed: 0.47 ft at 6:30PM Oct 01, 2023Observed: 0.26 ft at 6:36PM Oct 01, 2023Observed: -0.03 ft at 6:48PM Oct 01, 2023Observed: -0.17 ft at 6:54PM Oct 01, 2023Observed: -0.3 ft at 7:00PM Oct 01, 2023Observed: -0.38 ft at 7:06PM Oct 01, 2023Observed: -0.45 ft at 7:12PM Oct 01, 2023Observed: -0.49 ft at 7:18PM Oct 01, 2023Observed: -0.52 ft at 7:24PM Oct 01, 2023Observed: -0.52 ft at 7:30PM Oct 01, 2023Observed: -0.52 ft at 7:36PM Oct 01, 2023Observed: -0.45 ft at 7:48PM Oct 01, 2023Observed: -0.28 ft at 8:00PM Oct 01, 2023Observed: 9.34 ft at 3:24AM Oct 02, 2023Forecast: 5.8 ft 11:00AM Oct 02, 2023Forecast: 8.6 ft 12:00PM Oct 02, 2023Forecast: 10.6 ft 1:00PM Oct 02, 2023Highest Forecast: 11.3 ft 2:00PM Oct 02, 2023Forecast: 10.8 ft 3:00PM Oct 02, 2023Forecast: 9.1 ft 4:00PM Oct 02, 2023Forecast: 6.5 ft 5:00PM Oct 02, 2023Forecast: 3.7 ft 6:00PM Oct 02, 2023Forecast: 1 ft 7:00PM Oct 02, 2023Forecast: -0.7 ft 8:00PM Oct 02, 2023Forecast: -0.4 ft 9:00PM Oct 02, 2023Forecast: 1.2 ft 10:00PM Oct 02, 2023Forecast: 3.5 ft 11:00PM Oct 02, 2023Forecast: 6.1 ft 12:00AM Oct 03, 2023Forecast: 8.5 ft 1:00AM Oct 03, 2023Forecast: 10 ft 2:00AM Oct 03, 2023Forecast: 10.3 ft 3:00AM Oct 03, 2023Forecast: 9.2 ft 4:00AM Oct 03, 2023Forecast: 7.2 ft 5:00AM Oct 03, 2023Forecast: 4.9 ft 6:00AM Oct 03, 2023Forecast: 2.4 ft 7:00AM Oct 03, 2023Forecast: 0.6 ft 8:00AM Oct 03, 2023Forecast: 0.3 ft 9:00AM Oct 03, 2023Forecast: 1.7 ft 10:00AM Oct 03, 2023Forecast: 3.8 ft 11:00AM Oct 03, 2023Forecast: 6.2 ft 12:00PM Oct 03, 2023Forecast: 8.7 ft 1:00PM Oct 03, 2023Forecast: 10.5 ft 2:00PM Oct 03, 2023Forecast: 11 ft 3:00PM Oct 03, 2023Forecast: 10.1 ft 4:00PM Oct 03, 2023Forecast: 8.3 ft 5:00PM Oct 03, 2023Forecast: 5.9 ft 6:00PM Oct 03, 2023Forecast: 3.2 ft 7:00PM Oct 03, 2023Forecast: 0.8 ft 8:00PM Oct 03, 2023Forecast: -0.4 ft 9:00PM Oct 03, 2023Forecast: 0 ft 10:00PM Oct 03, 2023Forecast: 1.6 ft 11:00PM Oct 03, 2023Forecast: 3.7 ft 12:00AM Oct 04, 2023Forecast: 6 ft 1:00AM Oct 04, 2023Forecast: 8.4 ft 2:00AM Oct 04, 2023Forecast: 9.7 ft 3:00AM Oct 04, 2023Forecast: 9.6 ft 4:00AM Oct 04, 2023Forecast: 8.4 ft 5:00AM Oct 04, 2023Forecast: 6.7 ft 6:00AM Oct 04, 2023Forecast: 4.7 ft 7:00AM Oct 04, 2023Forecast: 2.5 ft 8:00AM Oct 04, 2023Forecast: 1.1 ft 9:00AM Oct 04, 2023Forecast: 1.3 ft 10:00AM Oct 04, 2023Forecast: 2.6 ft 11:00AM Oct 04, 2023Forecast: 4.6 ft 12:00PM Oct 04, 2023Forecast: 6.8 ft 1:00PM Oct 04, 2023Forecast: 9 ft 2:00PM Oct 04, 2023Forecast: 10.4 ft 3:00PM Oct 04, 2023Forecast: 10.7 ft 4:00PM Oct 04, 2023Forecast: 9.7 ft 5:00PM Oct 04, 2023Forecast: 8 ft 6:00PM Oct 04, 2023Forecast: 5.7 ft 7:00PM Oct 04, 2023Forecast: 3.2 ft 8:00PM Oct 04, 2023Forecast: 1.2 ft 9:00PM Oct 04, 2023Forecast: 0.3 ft 10:00PM Oct 04, 2023Forecast: 0.8 ft 11:00PM Oct 04, 2023Forecast: 2.1 ft 12:00AM Oct 05, 2023Forecast: 3.9 ft 1:00AM Oct 05, 2023Forecast: 6.1 ft 2:00AM Oct 05, 2023Forecast: 7.8 ft 3:00AM Oct 05, 2023NOAA Center for Operational Oceanographic Products and ServicesBHBM3(plotting HMIRG) Graph Created (10:00AM Oct 2, 2023)ObservedForecast (issued 4:06AM Oct 2)Latest observed value: 9.34 ft at 3:24 AM EDT 2-Oct-2023. Flood Stage is 12.5 ft
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About this graph
Tabular Data (UTC)
Tabular Data (EDT)
XML Data
RSS Files
Datum: Not Available
NOTE: Please refer to our Coastal Hazard Message for specific information regarding Coastal Flood Watches, Warnings and Advisories. Actual impacts from any coastal flooding event may vary due to factors such as rainfall, wave action, and the number of tide cycles during which there is an onshore flow. During tropical cyclones, please refer here for additional storm surge information.

NOTE: During a Tropical Storm or Hurricane Watch or Warning, inundation mapping provided by the National Hurricane Center (go to the web site and select the storm of interest) reflects a reasonable worst case scenario. The forecast above is the total water forecast that is most likely to occur.

NOTE: Forecasts for the Boston Harbor at Boston (IN MLLW) are issued routinely year-round.

Vertical Datum references a tidal datum...for more information see Tides and Currents .

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Flood Categories (in feet)
Major Flood Stage: 15
Moderate Flood Stage: 14
Flood Stage: 12.5
Action Stage: 11.5
Low Stage (in feet): -9999

Historic Crests
(1) 15.16 ft on 01/04/2018
(2) 15.10 ft on 02/07/1978
(3) 14.67 ft on 03/02/2018
(4) 14.20 ft on 01/02/1987
(5) 14.14 ft on 10/30/1991
(6) 14.04 ft on 01/24/1979
(7) 14.03 ft on 12/12/1992
(8) 13.97 ft on 12/23/2022 (P)
(9) 13.87 ft on 03/03/2018
(10) 13.84 ft on 12/29/1959
Show More Historic Crests

(P): Preliminary values subject to further review.

Recent Crests
(1) 12.56 ft on 06/06/2023 (P)
(2) 12.75 ft on 01/20/2023 (P)
(3) 13.97 ft on 12/23/2022 (P)
(4) 12.76 ft on 05/17/2022 (P)
(5) 12.97 ft on 01/29/2022 (P)
(6) 12.62 ft on 01/17/2022 (P)
(7) 12.82 ft on 01/03/2022 (P)
(8) 13.11 ft on 01/02/2022 (P)
(9) 13.25 ft on 02/02/2021 (P)
(10) 12.65 ft on 02/02/2021 (P)
Show More Recent Crests

(P): Preliminary values subject to further review.

Low Water Records
Currently none available.

For more information on your flood risk go to

Zoom Level:16
KML Image
Gauge LocationGauge Map Marker
Latitude/Longitude Disclaimer: The gauge location shown in the above map is the approximate location based on the latitude/longitude coordinates provided to the NWS by the gauge owner.
Flood Impacts & Photos Collapse
If you notice any errors in the below information, please contact our Webmaster
16 This is a degree of flooding rarely seen. Major widespread coastal flooding is expected. Numerous homes and roadways will be flooded from Revere and Winthrop southward thru Hull, including major flooding within the Boston Seaport District. Impacts will occur during several hours before and after high tide. People living in vulnerable coastal areas must take action to protect life and property.
14.5 Significant flooding of low lying coastal locations is expected from Revere and Winthrop southward through Hull. This includes significant flooding within the Seaport District of Boston. Numerous homes will be flooded. Road closures and evacuations of coastal sections are likely. Large swells and wave action will produce significant beach erosion.
14 Flooding of low lying coastal locations is expected from Revere and Winthrop southward through Hull. Road closures and some evacuations of coastal sections may be required. Large swells and wave action will produce minor to moderate beach erosion.
13.5 Minor flooding of low lying coastal locations is expected from Revere and Winthrop southward through Hull. The combination of high tides and large swells will result in washover onto coastal roadways and some road closures may occur around the time of high tide.
12.5 Minor coastal flooding occurs along Morrissey Boulevard in Boston.
(1) Boston Harbor Tidal Station
About This Location Collapse

Latitude: 42.353900° N, Longitude: 71.050300° W, Horizontal Datum: NAD83/WGS84

River Stage
Reference Frame
Gauge Height Flood Stage Uses
NWS stage 0 ft 12.5 ft Interpreting hydrographs and NWS watch, warnings, and forecasts, and inundation maps
Vertical Datum Elevation
(gauge height = 0)
(gauge height = flood stage)
Elevation information source
NAVD88 -5.51 6.99 Survey grade GPS equipment, FEMA flood plain maps, newer USGS topographic maps
NGVD 29 Not Available Not Available Older USGS topographic maps, NGVD29 benchmarks
MSL -5.21 7.29 Older USGS topographic maps, MSL benchmarks
Other Not Available 12.5 MLLW (Mean Lower Low Water)
Additional Information Collapse
**Coastal flooding can occur at a stage of 12 feet, when onshore winds are present along with 20 foot seas.** Boston Harbor gage data and forecasts are in feet Mean Lower Low Water (MLLW).
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Hydrologic Resources Additional Resources
Collaborative Agencies Collapse
The National Weather Service prepares its forecasts and other services in collaboration with agencies like the US Geological Survey, US Bureau of Reclamation, US Army Corps of Engineers, Natural Resource Conservation Service, National Park Service, ALERT Users Group, Bureau of Indian Affairs, and many state and local emergency managers across the country. For details, please click here.
NWS Information
National Weather Service
Boston / Norton Weather Forecast Office
46 Commerce Way
Norton, MA 02766
(508) 622-3250
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