Lightning Safety for Cyclists and Runners: The 30-30 Rule
Most weather risks on a ride are matters of comfort or pacing. Lightning is the exception — it is the one forecast item that can end badly in a single moment, and the one riders most often gamble on because the storm still looks a long way off. It usually isn't.
The 30-30 rule
Count the seconds between the flash and the thunder. Sound covers about a mile every five seconds, so thirty seconds means the strike was roughly six miles away — and that is already within range of the next one, because lightning regularly jumps ten miles from the storm that produced it.
So: at thirty seconds or less, stop looking for a better option and take the best shelter available. Then wait thirty minutes after the last rumble of thunder before heading out again. The tail end of a storm is when most people get caught, because the rain stops and the sky brightens well before the charge does.
If you can hear thunder at all, you are close enough to be struck. That is the whole rule in one sentence.
What counts as shelter — and what doesn't
Safe: a substantial enclosed building with wiring and plumbing, or a hard-topped vehicle with the windows up. A support car, a shop, a house.
Not safe: a picnic pavilion, a dugout, a bus stop with an open side, a bridge underpass, and above all a tree. Standing under an isolated tall tree is one of the most common ways people are struck, because the current jumps sideways to the person beside the trunk.
Your bike does not attract lightning — metal doesn't draw strikes, height and isolation do. But a bike gives you no protection either, and riding a wet road at speed while flinching at thunder is its own hazard. Get off it.
- A substantial enclosed building with wiring and plumbing
- A hard-topped vehicle with the windows up
- A tree — the current jumps sideways to whoever is beside the trunk
- A picnic pavilion, a dugout, an open-sided bus stop
- A bridge underpass
- Your bike: metal doesn't attract strikes, but it protects you from nothing
When there's genuinely nowhere to go
Get off exposed high ground and away from open water, fences, metal railings, and anything tall standing alone. A low-lying spot among uniformly short trees is better than a hilltop or a lone oak.
Spread out if you're in a group so one strike can't take everyone, and don't lie flat — ground current travels through the surface and lying down maximises your contact with it. Crouching low with your feet together is the least-bad posture, and it is a last resort, not a plan.
The real answer is upstream: summer storms build on a schedule. Watching the radar before an afternoon ride is worth more than any technique for surviving one.
The takeaway
Thunder within thirty seconds means shelter now; thirty minutes after the last thunder means it's over. Nothing outdoors is safe shelter — not a pavilion, not an underpass, and never a tree. RideByWeather's storm alerts flag lightning risk in your window before you leave.
Check today's Ride ScoreFrequently asked
What is the 30-30 rule for lightning?
If the gap between the lightning flash and the thunder is thirty seconds or less, the storm is close enough to strike you — take shelter immediately. Then wait a full thirty minutes after the last thunder before going back out.
How far away can lightning strike from a storm?
Lightning regularly travels ten miles or more from the storm cloud that produced it, which is why strikes happen under clear-looking sky. If you can hear thunder, you are within range.
Is it safe to shelter under a tree or a bridge during a thunderstorm?
No. A lone tree is one of the most dangerous places to stand — the current jumps sideways from the trunk to anyone beside it. Bridges, pavilions, and open bus shelters offer no protection either. Only a substantial enclosed building or a hard-topped vehicle is safe.
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