Calculate how far away a storm is based on the time between flash and thunder.
Storm Observations
seconds
°C
Distance Results
Enter time delay to calculate storm distance
About this calculator
Quick Reference
Speed of Sound (20°C)343 m/s
1 km~3 seconds
1 mile~5 seconds
Light SpeedToo fast to count!
Overview
Because light travels much faster than sound, you see a lightning flash almost instantly, but the sound of the thunder takes time to reach you. By measuring this delay, you can estimate the distance to the strike.
💡
Pro Tips
Light travels at ~300,000 km/s (instant for local storms).
Sound travels at ~343 m/s (approx. 1 km every 3 seconds).
A common rule of thumb is '5 seconds per mile'.
!
Fun Facts
"Wait, did you know that lightning is five times hotter than the surface of the Sun? It's the sudden expansion of air due to this extreme heat that creates the 'sonic boom' we call thunder."
"The longest recorded lightning bolt was over 700 kilometers (440 miles) long, stretching across several US states!"
"If you hear thunder at the same time you see the flash, the lightning hit extremely close (Stay safe!)."
