Calculators
Distance to Lightning from Thunder
From the delay between the flash and the thunder
Reminder
Start counting seconds at the flash and stop at the first rumble of thunder. Every 3 seconds is about 1 kilometre. Under 30 seconds means the storm is close — better get indoors.
Result
Enter the values and the result will appear here.
Formula
343 m/s is the speed of sound in air at +20 °C (about 331 m/s at 0 °C), t is the thunder delay, s is the distance to the lightning.
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History
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Частые вопросы
How do I find the distance to lightning?
Count the seconds from the flash to the first rumble of thunder and multiply by 343 m/s, the speed of sound. Every 3 seconds is about 1 kilometre.
Why exactly 343 metres per second?
It is the speed of sound in air at +20 °C. In frost sound is slower (about 331 m/s at 0 °C) and the distance comes out slightly smaller. The speed of light can be ignored.
When is a storm dangerous?
If less than 30 seconds pass between flash and thunder (about 10 km), the storm is close — better get into a building or a car.
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