About
How our forecasts work
Every forecast on this site is generated automatically from professional weather and ocean models, then interpreted for each surf spot using its orientation, swell window, preferred winds and tides.
Data sources
- Swell, waves, wind and weather: Vaisala Xweather Maritime API: significant wave height, primary and secondary swell trains, sea surface temperature and tide levels. Vaisala Xweather Forecasts API: hourly wind, gusts, temperature and weather.
- Sunrise and sunset: calculated from standard solar equations for each beach.
- Tides: modelled sea level from the marine model (or official UK Hydrographic Office predictions where configured). Tide times are indicative and not for navigation.
- Sea temperature: modelled sea surface temperature at the forecast point.
Update schedule
Forecasts refresh automatically twice a day at 06:00 and 18:00 UTC (07:00 and 19:00 during British Summer Time), shortly after the main model runs become available. Processed forecasts are cached for up to 12 hours, so the site stays fast and we only make a handful of requests to our data providers each day. If a provider is unavailable we keep showing the last good forecast and clearly label it.
Surf size
Wave models forecast deep-water swell height. We convert that into an estimated breaking wave face height at each beach, accounting for:
- Swell period — long-period groundswell breaks much bigger than short-period windswell of the same height.
- Swell direction — swell from outside a spot's swell window is blocked or heavily reduced.
- Local calibration — some beaches break bigger or smaller than the open-ocean swell suggests.
Sizes are shown in feet as a range of typical waves to the bigger sets.
Surf rating
Each hour is scored from 0 to 10 by combining:
- Size (38%) — how the surf compares with the spot's ideal range.
- Wind (32%) — offshore is best, onshore worst, and strength matters.
- Period (20%) — longer period means more powerful, better-organised waves.
- Swell direction (10%) — how squarely the swell hits the spot.
- Tide — the wrong stage of tide reduces the score at tide-sensitive spots.
Flat or blown-out conditions are capped, so one good factor can't hide a fatal flaw. A day's rating is the average of its three best daylight hours.
| ★ | Poor | Flat, tiny or blown out. Not worth the trip. |
|---|---|---|
| ★★ | Fair | Surfable but compromised — small, short-period or windy. |
| ★★★ | Good | Fun waves with decent size and reasonable wind. Worth a session. |
| ★★★★ | Excellent | Quality surf: good size, solid period and clean, offshore-ish winds. |
| ★★★★★ | Epic | Everything lines up. Call in sick. |
Wind
Wind is classified relative to each beach: offshore (blowing from the land, grooming the waves), cross-offshore, cross-shore and onshore (blowing from the sea, making the surf choppy). Under about 3mph conditions are glassy whatever the direction.
Best surf window and skill levels
The best surf window is the run of daylight hours around the day's peak that stay close to it in quality, together with the stage of tide at the peak. Skill suitability considers wave size, wind, overall quality and whether the spot is a sand-bottom beach or a reef.
Stay safe
Forecasts are a guide, not a guarantee. Always check conditions on arrival, surf at lifeguarded beaches between the black-and-white flags, and never surf beyond your ability. In an emergency at the coast call 999 and ask for the Coastguard. Visit the RNLI for beach safety advice.