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Home › Survival calculators › How far away is the lightning?

How far away is the lightning?

Count the seconds from the flash to the thunder.

How it works

Light arrives almost instantly, but sound travels about 343 metres a second (at 20 °C). So every 3 seconds is about a kilometre, and every 5 seconds about a mile.

When thunder roars, go indoors

Lightning can strike as far as 10 miles (16 km) from a storm — about as far as you can hear thunder. The US National Weather Service's advice is simple: if you can hear thunder, you are close enough to be struck. Get inside a building with wiring and plumbing, or a hard-topped metal vehicle with the windows closed, and stay there until 30 minutes after the last thunder. Sheds, tents, picnic shelters and covered porches do not protect you.

If you are caught outside with nowhere to go, get off high ground, away from tall isolated trees and water, and keep moving towards shelter.

For planning and general information. In an emergency, follow the instructions of your local authorities and call your emergency number (911, 112, 999 or 000).

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Source: NOAA JetStream, Lightning Safety (US National Weather Service).