Reading Weather and Wind Windows for Crossings

Planning 10 min read · Updated May 2026

How expedition paddlers identify a safe weather window for crossings - and when to wait, even at the cost of days.

The crossing decision

Open-water crossings are the highest-risk component of most coastal expeditions. The Bay of Biscay, the North Channel, the Strait of Georgia, the Drake Passage. These crossings cannot be aborted partway. The decision to start must be the right one.

The two-day weather window

The standard rule: a meaningful open-water crossing requires a forecast window of at least double the crossing duration. A 12-hour crossing requires 24+ hours of stable forecast. This allows for arrival delay, surface conditions developing slower than forecast, or extending into the next morning if needed.

Forecasts to cross-reference

Three or more model sources before crossing: Met Office for British waters, ECMWF (via Windy.com), GFS (also Windy), and where available Predictwind premium for offshore work. If three sources agree, the forecast is reliable. If they diverge, postpone.

Sea state vs wind speed

Wind speed alone is not the metric. Significant wave height, swell direction, and tide-against-wind effect matter as much. A 15-knot wind with 4-metre swell from the wrong angle is harder than 25 knots with calm swell. Look at the whole picture, not just the wind.

The wait

Many successful expeditions involved 5-12 day waits for the right window. The paddler who sat out 8 days in Cape Wrath knowing the autumn weather would not give a second chance is the paddler who finished. Patience is not weakness; it is the skill that separates the expedition from the holiday.