Grafham Water

Current conditions refresh every 3 hours when the conditions cron runs. Sub-scores are recalculated from the latest hourly data each time you load the page.

Club Dinghy scoring is optimised for boats like the Laser, RS200, and Wayfarer that peak at 14-16 knots. High Performance scoring suits boats like the 49er, Moth, and RS800 that want 18-20 knots and tolerate stronger winds.

The algorithm slides a 4-hour window through racing hours (09:00-18:00) and picks the window with the highest score. The day's score weights this window at 70%, so a perfect afternoon sea breeze is not punished by a glassy morning.

Sustained winds above 40 knots, gusts above 50 knots, or visibility below 500m trigger automatic suppression, with the reason shown on the page. Thunderstorms no longer suppress the score: the score rates the sailing conditions themselves, and storms appear as a separate red safety flag instead.

Red and amber indicators for thunderstorms, convective storm risk, extreme wind, and poor visibility. They are computed separately from the score, so a windy pre-frontal day can score well for conditions while still carrying a clear do-not-launch warning.

Open-Meteo Weather API for wind, temperature, pressure, and visibility. Open-Meteo Marine API for wave and swell data at coastal and estuary venues.