How BoatCast works

BoatCast combines forecast data and boating-focused rules to turn several conditions into one easy-to-understand rating.

BoatCast is provided for general informational and planning purposes only. It is not a substitute for official weather and marine forecasts, observations, alerts, watches, warnings, advisories, notices, or instructions from NOAA, the National Weather Service, the U.S. Coast Guard, emergency authorities, or other official sources. Always review current official information and actual local conditions before and during any boating activity.

When an official warning is active near your pin, BoatCast surfaces it prominently and will not present a casual “Go” treatment even if some model inputs look favorable. Full text: Forecast & Safety Disclaimer.

What the rating represents

• The rating is for the weather zone around your selected point (about a 10-mile grid cell), not every cove or channel inside that zone.
• Day cards (Today / Tonight / later days) vote remaining hourly conditions in that card’s time window.
• Overall hour rating uses the worst limiting factor among weather, wind, visibility, waves/swell, and (when seas are not flat) wave period.

Inputs that affect the rating

• Sky / precip: drizzle and fog tend toward Fair; rain, snow, and thunderstorms rate Poor. Thunderstorms also include rain/shower hours with high CAPE (≥ 1000 J/kg) when the model does not emit an explicit storm code.
• Wind: Good under 15 mph, Fair 15–25 mph, Poor over 25 mph (sustained).
• Visibility: Good above 5 nautical miles, Fair 2–5 NM, Poor under 2 NM (NWS/IMO-style bands). Period cards use the minimum visibility in the window.
• Waves / chop: height is scored against regional typical wave height (coastal regions differ; lakes use Great Lakes–style norms). Roughly within ~1× typical is Good; much higher becomes Fair then Poor.
• Swell: scored on ocean / coastal points; skipped for lake source.
• Wave period: compared to regional typical bands (for example Southeast Atlantic ~4–8s, Southern California ~8–14s). Periods shorter than the band can rate Fair/Poor (“short-period chop”). Flat seas under ~0.15 m skip period scoring. Longer-than-typical period is treated as Good.
• Gusts, rain chance, clouds, feels-like: shown in detail views; they inform the picture but the headline rating is driven by the factors above.

Lakes vs coastal water

If Open-Meteo Marine has wave/swell at the pin, BoatCast treats the spot as ocean. Otherwise it uses lake mode: wind-based chop estimates and lake water-temperature methods (satellite SST when available, otherwise regional shore-air memory). Swell is not scored on lakes.

How wind direction relates to chop

Lake chop height is estimated from wind speed (and related marine fields when present). Direction is shown so you can judge fetch and lee shores yourself; the automated rating does not yet model shoreline-specific wind waves for every cove.

Update frequency

• Assembled BoatCast forecasts are cached about 45 minutes per weather zone.
• Underlying Open-Meteo air/marine bundles may be reused up to about an hour.
• Live radar at the pin refreshes on a shorter cadence (~3 minutes) for the Now card.
• Official NWS alerts are checked separately on a short cache (~3 minutes).

The day card shows when BoatCast last built the forecast for that zone (“Forecast updated … ago”).

Why BoatCast may differ from NOAA, Windy, or another app

• Different model grids and blend choices (Open-Meteo vs NWS grids).
• BoatCast collapses many variables into one recreational-boating score with fixed thresholds — other apps emphasize different hazards.
• Zone averaging (~10 mi) can miss microclimates, passes, and river mouths.
• Lake water temperature and chop are estimates when dedicated marine fields are missing.

What “AI” means here

BoatCast uses automated rules and model outputs — not a black-box “AI says go” judgment. Marketing may mention AI-assisted tooling in development; the rating you see is deterministic from the published thresholds above. We do not claim to be the most accurate weather source without published verification studies.

Data sources

• Weather forecast: Open-Meteo
• Marine / water: Open-Meteo Marine when wave/swell is available; otherwise Open-Meteo air plus wind-based lake estimates
• Water temperature (when used): NOAA GLSEA, JPL MUR, Copernicus LSWT, or regional shore-air / model estimate
• Map / places: OpenStreetMap Nominatim
• Radar: RainViewer
• Official alerts: National Weather Service (api.weather.gov)

Questions or a rating that looks wrong? Report a forecast or email support@boatcastapp.com.