A thunderstorm can change local wind and visibility much faster than a broad-area daily forecast suggests. Lightning, steep short waves, hail and waterspouts may accompany it. A forecast for the whole sea area cannot tell you exactly which boat will meet a particular cell.
Before departure: check more than the daily icon
Read the latest official marine forecast and short-fuse warnings for the exact area. Look for instability, a cold front, squall lines and language about thunderstorms or sudden gusts. Where available, examine recent observations and radar, then check whether the cell is moving toward your route. Radar is a short-term aid, not a guarantee of a clear passage; it may be unavailable offshore or miss hazards.
Prefer shelter while there is still time
If storms are expected during a short recreational trip, delaying or staying ashore may be the simplest safe choice. If already afloat, identify a reachable safe harbour or sheltered area before conditions deteriorate. Do not steer through a storm merely because a model shows a narrow gap. Recheck the official warning and actual conditions.
Prepare early, not at the first gust
Brief the crew, secure loose items and hatches, put on appropriate personal flotation, and reduce sail in good time according to the vessel’s procedures. Keep an effective lookout and be ready for a rapid visibility change. During lightning, avoid unnecessary contact with exposed metal or electrical equipment; do not assume a mast or lightning system makes the boat safe. Follow the vessel’s lightning procedures.
After the cell passes
Do not treat one lull as an all-clear: further cells or a new warning may follow. Recheck the sky, sea state, equipment and position, then decide whether the original destination is still sensible. The skipper retains responsibility for the manoeuvre and for calling for assistance if safety is in doubt.
Official sources
Important: This is practical passage guidance, not a forecast for your specific departure or a navigational route. Personalised forecasts with AI and experts are in closed testing. Before and during a passage, check the latest official forecasts and warnings for your area; the skipper decides in light of actual conditions, vessel and crew.
Three clocks on a radar screen
Check image time, the age of the latest frame and the time needed to reach the exposed leg. Every radar image has some delay; a stalled animation or missing recent frames must not be treated as live coverage. Watch whether the official warning changes while you interpret cell motion; a broad forecast or empty patch on a radar display cannot guarantee the absence of lightning or a sudden gust.
- NWS: boating and thunderstorms — Thunderstorm and lightning hazards to boats.
Prepare roles as well as sails
Before workload increases, identify who handles the boat, who keeps the lookout, who receives updates and who checks the crew. Agree how a plan change will be communicated in reduced visibility and noise. Do not rely on a universal reefing threshold or storm-avoidance course: both need the boat’s procedures and the real situation.
Editorial review of this material: 27 September 2026. This date concerns the page content; check current forecast issue times and validity at the original sources.