Reading the Weather Before a Sail

A layered approach to going or not going

Before any sail, three layers of information tell you whether the day is sailable: the marine forecast, the radar picture, and the sky above you. None of the three alone is enough.

The marine forecast

The US National Weather Service issues marine forecasts for every coastal and Great Lakes zone. Read the forecast for wind speed, gusts, wind direction, wave height, and any small-craft advisory. Forecasts are typically reliable for the next 24 hours, less reliable beyond that.

A small-craft advisory means wind speeds or seas have reached a level dangerous for small boats; respect it.

Radar

Smartphone weather apps and the NWS radar page show precipitation in real time. Before leaving the dock, look at the radar for the next 2–4 hours and identify any approaching storm cells. A line of thunderstorms 50 miles upwind will reach you in roughly two hours at typical front speeds.

The sky and the water

Once on the water, the sky is your best forecaster:

• Towering cumulus building vertically often means a thunderstorm is forming.
• Mares' tails (cirrus clouds in long streaks) usually precede a front in 24–48 hours.
• Sudden temperature drop or wind shift means a front is passing now.
• Dark line on the horizon approaching from upwind is often a squall — reduce sail and head for shelter.

When in doubt, stay in

The cost of canceling a sail is one missed afternoon. The cost of going out in a thunderstorm is everything else. If you are uncertain, do not go.

Takeaways

• Read the marine forecast for wind, waves, and advisories.
• Check radar for any cells within 2–4 hours.
• Read the sky once on the water — clouds, temperature, and the horizon.
• When in doubt, stay in.