Lightning: make the safe-shelter decision

Hear thunder? Move to shelter

Lightning can strike outside the part of a storm producing heavy rain. Do not use a blue patch of sky or dry ground as proof that the danger has passed. If thunder is audible, suspend outdoor activity and move promptly to safer shelter.

A forecast check is part of the trip plan, but conditions can develop quickly. Turnaround times should include the walk back to a building or vehicle. On exposed ridges, water, and open terrain, that margin needs to be generous.

What counts as safer shelter?

1. A substantial building. Choose an enclosed structure with wiring and plumbing when available. Move away from windows and exterior doors.
2. A hard-topped enclosed vehicle. Close the windows. Avoid touching conductive paths connected to the exterior.
3. Inside the building. Avoid corded electrical equipment, plumbing, concrete walls or floors where practical, and windows during the storm.

Picnic shelters, open pavilions, porches, tents, lean-tos, and isolated trees do not provide the protection of a substantial enclosed building. A tent may keep out rain; it does not make lightning safe.

If safer shelter is unavailable

No outdoor action removes the risk. Move away from summits, ridgelines, isolated tall objects, open fields, water, wire fences, and other conductive features when you can do so without creating another hazard. Do not shelter beneath an isolated tree.

If a group is caught outside, spreading out can reduce the chance that one strike injures everyone, while remaining close enough to communicate and respond. Avoid lying flat on the ground. These steps are risk reduction, not a replacement for shelter.

Wait 30 minutes after the last thunder

NOAA recommends waiting at least 30 minutes after the last sound of thunder before returning outside. Restart the clock if thunder returns. The trailing edge of a storm can still produce dangerous lightning.

For organized trips, assign one person to monitor weather and make the stop decision. This reduces the social pressure to keep going when every person assumes someone else is watching.