Lightning distance

Count the seconds from flash to thunder, divide by 3 for kilometres (by 5 for miles).

Why it works

Sound travels ~343 m/s, so ~3 s per km and ~5 s per mile. Light arrives effectively instantly.

More in Environmental

• Air cools as you climbTemperature drops about 6.5 °C for every 1,000 m of altitude.
• Pressure halves every ~5.5 kmAtmospheric pressure falls by half roughly every 5,500 m you climb.
• Ten metres of water = one atmosphereEvery 10 m of seawater adds about 1 atmosphere of pressure.
• Boiling point falls with altitudeWater boils about 1 °C cooler for every 300 m of altitude.

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