Plymouth Harbor
Doable, but keep one eye on the sky and the other on the chop.
Mostly Clear · 80° · 5 kt windSmall Craft Advisory issued July 17 at 12:38PM EDT until July 19 at 12:00PM EDT by NWS Boston/Norton MA In effect through 7/19/2026, 12:00:00 PM EDT.
Read the NWS alertSmall Craft Advisory is active. Boat or Nope keeps this window at Caution even when the forecast remains inside your boat limits.
For Pursuit 235 · 4 hours · limits 15 kt / 2.5 ftMake it yours, skipper
The flag re-reads the water for your boat and your day.
Your boat
Time on the water
Your comfort line: 15 kt wind · 2.5 ft seas
Pick your day
Seven days, one honest flag each.
Showing hourly detail for today. Each flag uses that day's own forecast.
Daylight forecast
6 NWS grid hours
2 ft at 3 sec · 84°
4 turns today
Tide stage shown as a proxy; no speed inferred
Selected station has no recent observation
NDBC 44013
NDBC 44013 · observed 7/17/2026, 5:10:00 PM EDT
How the day develops
Wind, waves, and tide stay aligned to the same daylight hours.
Sustained wind in knots. The dashed line is your selected boat limit.
Wave height from the NWS marine grid, with clearly identified buoy-based estimates for gaps.
Predicted water level in feet relative to MLLW from NOAA CO-OPS.
Hour by hour
Daylight only. The useful part of your day.
8 kt
2 ktView exact hourly readings
How this forecast is built
6 of 8 inputs reporting. Stations, locations, and roles are shown below.
Resolved directly from the destination coordinates.
The buoy fills wave gaps and supplies observations.
Predicted heights, turns, and current speed where supported.
1 active notice.
Measured-versus-predicted check unavailable.
Latest available buoy observation.
Source geography
Where these readings come from
Dashed lines connect this destination to the stations contributing marine, tide, and aviation context.
- Forecast pointPlymouth HarborNWS forecast point
- BuoyBoston · 4401323.2 NM away
- Marine gridCape Cod Bay · 4401826.9 NM away
- Tide gaugeSandwich Marina · 844718013.2 NM away
- AviationBoston/Logan Intl · KBOS28.9 NM away
NWS hourly forecast
RoleSupplies the hourly wind, sky, temperature, and precipitation forecast at this destination.
- forecast point
- Plymouth Harbor · plymouth-harbor
- Coordinates
- 41.9600° N, 70.6600° W
Why this sourceResolved live from the destination coordinates, so it represents the selected harbor rather than a nearby city.
Data timingForecast grid updated · 3 hr ago
ConfidenceThe forecast is resolved directly at this location.
Hourly wind, weather, temperature, and precipitation forecast resolved from the selected latitude/longitude.
NWS active marine hazards
RoleChecks active watches, warnings, advisories, and statements and applies their severity to the boating verdict.
- alert point
- Plymouth Harbor · plymouth-harbor
- Coordinates
- 41.9600° N, 70.6600° W
Why this sourceResolved directly at the destination coordinates through the NWS active-alert feed.
Data timingAlert feed updated · just now
ConfidenceThe forecast is resolved directly at this location.
1 active National Weather Service alert intersects the selected point.
NWS coastal marine grid
RoleSupplies forecast wave heights, which Boat or Nope uses before buoy-based estimates when available.
- marine grid point
- Cape Cod Bay · 44018
- Distance
- 26.9 NM from destination
- Coordinates
- 42.2030° N, 70.1540° W
Why this sourceResolved on the coastal marine grid at 44018, the selected marine reference point for this destination.
Data timingMarine grid updated · 3 hr ago
ConfidenceThe source is 26.9 NM away, so local conditions may differ.
Wave-height forecast resolved at marine reference 44018. Used before Boat or Nope's observed-buoy fallback when the grid reports usable wave heights.
NDBC 44013
RoleChecks recent observed wind, waves, and water temperature and helps fill gaps when the marine grid has no usable wave value.
- buoy
- Boston · 44013
- Distance
- 23.2 NM from destination
- Coordinates
- 42.3460° N, 70.6510° W
Why this sourceThe configured buoy 44018 did not report usable observations, so 44013 was selected from nearby candidates.
Data timingLatest buoy observation · 32 min ago
ConfidenceThe selected source is within 25 NM of the destination.
Automatic fallbackConfigured 44018; selected 44013 after checking 44018, 44013.
Selected catalog buoy, 23.2 NM from the selected location. Reports observed wind, waves, and water temperature when those sensors are available.
CO-OPS 8447180
RoleSupplies predicted tide heights and high/low timing for each forecast day.
- tide station
- Sandwich Marina · 8447180
- Distance
- 13.2 NM from destination
- Coordinates
- 41.7717° N, 70.5067° W
Why this sourceThe configured tide gauge 8443970 did not return complete predictions, so 8447180 was selected from nearby candidates.
Data timingPredictions generated for each selected day
ConfidenceThe selected source is within 25 NM of the destination.
Automatic fallbackConfigured 8443970; selected 8447180 after checking 8443970, 8447180.
Selected catalog tide station, 13.2 NM from the selected location. Tide predictions and high/low events in feet relative to MLLW for the available forecast days.
CO-OPS observed water level 8447180
RoleCompares the latest measured water level with the predicted tide to reveal material positive or negative departures.
- water-level station
- Sandwich Marina · 8447180
- Distance
- 13.2 NM from destination
- Coordinates
- 41.7717° N, 70.5067° W
Why this sourceUses the same selected CO-OPS station as the tide forecast so observed and predicted heights share the MLLW datum.
Data timingNo recent water-level observation
ConfidenceNearby candidates were checked, but none returned usable data during the latest refresh.
Checks whether the selected CO-OPS station reports a recent measured water level that can be compared with prediction.
CO-OPS water level: The operation was aborted due to timeout
CO-OPS tidal currents
RoleSupplies predicted flood, ebb, and slack timing and speed for wind-against-current risk checks when NOAA supports the nearby station.
- current search point
- Plymouth Harbor · plymouth-harbor
- Coordinates
- 41.9600° N, 70.6600° W
Why this sourceNo nearby mapped station returned predictions during this refresh; no current speed is inferred from tide height alone.
Data timingPrediction unavailable
ConfidenceNearby candidates were checked, but none returned usable data during the latest refresh.
Boat or Nope only shows current speed when a nearby NOAA prediction station returns usable flood, ebb, or slack data; tide stage remains clearly labeled as a proxy otherwise.
CO-OPS currents: ACT1556: The operation was aborted due to timeout
AviationWeather KBOS
RoleAdds nearby observed and forecast gust context from METAR and TAF reports.
- aviation station
- Boston/Logan Intl · KBOS
- Distance
- 28.9 NM from destination
- Coordinates
- 42.3656° N, 71.0096° W
Why this sourceChosen from the nearest aviation candidates that returned a current METAR or TAF report.
Data timingLatest METAR observation · 3 hr ago
ConfidenceThe source is 28.9 NM away, so local conditions may differ.
Nearest aviation candidates: KBOS 28.9 NM, KPVC 20.7 NM, KEWB 21.6 NM, KHYA 24.4 NM.
Hourly seas: NWS coastal marine-grid wave height is preferred when available. Gaps fall back to the latest NDBC wave observation projected with forecast wind; fallback values are planning estimates, not NOAA wave forecasts.
Wave character: Wave height and dominant period are combined to distinguish long-period swell from short or steep chop. The label explains comfort and handling; it is not a replacement for a vessel-specific stability assessment.
Current and water level: Current speed is shown only when a nearby NOAA current-prediction station returns usable data. Observed water level is compared with the same station's MLLW tide prediction; tide stage is not presented as measured current speed.
Verdict: Go, Caution, No-Go, or Incomplete uses your wind and sea limits, then applies official active-alert severity and identified wave/current compound risks.
Source retrieval16 reused · 11 refreshed · 1 known outage skipped
Updated 7/17/2026, 5:41:45 PM EDT · Planning context, not certified navigation.
Local source coverage
Planning a boating day at Plymouth Harbor
A broad but shoal harbor system shared with Kingston and Duxbury, entered through a long marked channel.
This harbor in Massachusetts uses Cape Cod Bay (44018) for marine observations, Boston (8443970) for tide predictions, and Boston/Logan Intl (KBOS) for nearby aviation weather context.
This location is part of Boat or Nope's reviewed launch catalog and remains subject to automated source-health checks.Nearby harbors