Arithmetic, time and navigation
Distance to a storm from the thunder
Calculates how far away a lightning strike hit from the seconds between the flash and the thunder.
Tool
Tools › Arithmetic, time and navigation
How it is calculated
Light arrives almost instantly; sound takes time. Speed of sound c = 331.3 + 0.606 × T (°C) m/s. Distance = c × seconds.
Example: at 20 °C, c = 331.3 + 0.606 × 20 = 343.4 m/s. If 5 s pass between the flash and the thunder, the distance is 343.4 × 5 = 1717 m (1.72 km).
Keep in mind
- Practical approximation without a stopwatch: every 3 seconds is a bit less than 1 km (about 970 m at 15 °C).
- Count from when you see the flash, not from when the storm started: each strike is a separate calculation.
- Below 30 s, take shelter immediately: the next strike could land where you are.