Boat size is context, not a threshold calculator
A small training dinghy, a ballasted keelboat and a larger cruising boat behave differently, but length alone does not establish a suitable maximum wind. Sail plan, maintenance, load, crew and operating area all matter. This page therefore does not manufacture a table that declares a safe limit for every boat length.
For a small open boat, shelter and the ability to return can dominate the plan. On a larger vessel, the passage, sail handling, crew readiness and conditions at the destination still matter. Neither case is solved by a single positive weather score.
The return passage is part of the forecast
Check the entire time afloat and the approach to harbour, including delays. Wind direction and tide can make a route very different from the conditions inside a marina. The model does not calculate waves or a vessel’s ability to make progress in a particular direction.
The explorer keeps mean wind and gusts separate and explains that the sailing score uses gusts when supplied. It is not a naval-architecture model or a reefing schedule. A favourable score cannot replace the skipper’s decision or official marine warnings.
Worked examples from the existing scorer
These complete hypothetical hours run through the same scoring functions used by the live tool. They are not observations or forecasts. The displayed effective score includes any cap.
| Example | Effective score | Verdict | Model reasons |
|---|---|---|---|
| Gusts 35 km/h | 100/100 | GO | No model penalties |
| Gusts 43 km/h | 64/100 | MAYBE | strong — reef down · MAYBE cap |
| Gusts 53 km/h | 40/100 | NO-GO | gale-force wind · NOGO cap |
Exact example inputs and units
temp and feels: °C; wind and gust: km/h; precipitation: mm/h; visibility: m; rain probability, cloud and humidity: %. Weather code is WMO; UV is an index. Pressure, where shown, is context in hPa and does not affect this scorer.
[
{
"example": "Gusts 35 km/h",
"inputs": {
"temp": 15,
"feels": 15,
"precip": 0,
"pop": 0,
"wind": 25,
"gust": 35,
"vis": 20000,
"code": 0,
"cloud": 10,
"humidity": 60,
"uv": 0,
"pressure": 1010
}
},
{
"example": "Gusts 43 km/h",
"inputs": {
"temp": 15,
"feels": 15,
"precip": 0,
"pop": 0,
"wind": 30,
"gust": 43,
"vis": 20000,
"code": 0,
"cloud": 10,
"humidity": 60,
"uv": 0,
"pressure": 1010
}
},
{
"example": "Gusts 53 km/h",
"inputs": {
"temp": 15,
"feels": 15,
"precip": 0,
"pop": 0,
"wind": 35,
"gust": 53,
"vis": 20000,
"code": 0,
"cloud": 10,
"humidity": 60,
"uv": 0,
"pressure": 1010
}
}
]Planning bands and the limits of the number
The existing model starts at 100, subtracts its condition penalties and applies critical caps. GO is 70–100, MAYBE 45–69 and NO-GO 0–44. A MAYBE cap limits the effective score to 64, and a NO-GO cap to 40. These are application suitability bands, not certified safe operating limits.
Rain branches are alternatives: matching probability, intensity and weather-code triggers do not mean adding the same rain penalty repeatedly. Separate factors can combine. A cap prevents benign temperature or dry weather from cancelling a critical flagged condition. Use the reasons beside the result to understand what changed.
The model requires complete numeric weather inputs. Missing visibility, rain probability or another required value returns Insufficient data; it is never filled with an invented favourable value. Local warnings, closures, equipment instructions and actual observations can change your decision even when the model returns GO.
Read the full sailing methodology and thresholds. The model and these examples were cross-checked on 18 October 2026. No physical field-test or safety certification is claimed.
Equipment and an alternative plan
Use the actual boat’s guidance, prepare the crew and a practical return plan, and check marine conditions and tides. Follow RNLI preparation advice and appropriate local information. Change the passage or stay ashore when conditions exceed the boat, crew or plan.
Questions about Too windy to sail? Boat size, gusts and a passage decision
Does the score adjust for boat length?
No. Boat size is not a scorer input.
Does a GO include waves and tides?
No. Those need separate marine information.
Are 42 and 52 km/h manufacturer limits?
No. They are existing application cap boundaries.
Sources and limits
The numeric application bands come from the existing GoNoGo scorer and methodology. External guidance is linked for its stated context; it is not presented as endorsement of this model.
Live forecast data is supplied by Open-Meteo. An illustrative model output is different from a live forecast, and a forecast is different from a local observation.