Lightning Distance
Calculator
Results
- Distance (km)
- 3.088931
- Distance (miles)
- 1.919373
- Speed of sound (m/s)
- 343.214622
Weather results
| Distance (km) | 3.088931 |
| Distance (miles) | 1.919373 |
| Speed of sound (m/s) | 343.214622 |
formula-map diagram
- Distance (km)
- 3.088931
- Distance (miles)
- 1.919373
- Speed of sound (m/s)
- 343.214622
Weather relationship
Formula
d = c × Δt, c = 331.3 × √(1 + T ÷ 273.15) m/s (speed of sound in dry air)= 3.0889316041431
Note
This is a simplified model: it applies the published standard formula to the numbers you entered and ignores local terrain, radiation, precipitation type and instrument error. Wind chill is the 2001 NWS/Environment Canada regression, valid at or below 10 °C with wind at or above 4.8 km/h; the heat index is the Rothfusz regression, reliable above about 27 °C; dew point uses the Magnus approximation (a = 17.27, b = 237.7 °C) over liquid water; wet bulb uses Stull's approximation at standard sea-level pressure; pressure and density altitude assume the International Standard Atmosphere and dry air. Do not use these results for aviation, structural or safety decisions without an official forecast or a qualified professional.
More in Weather and climate
See all →Frequently asked questions
How does this calculator estimate how far away lightning struck?+
It uses the time delay between seeing the lightning flash and hearing the resulting thunder, multiplied by the speed of sound in air, since light reaches an observer essentially instantly while sound travels at a known, much slower, fixed speed.
What is the commonly used 'flash to bang' rule?+
A widely used shortcut is dividing the count of seconds between the flash and the thunder by 5 to get the distance in miles (or by 3 to get the distance in kilometres), based on the approximate speed of sound in typical air conditions.
Why does this method assume the flash is seen instantly?+
Light travels at roughly 300,000 kilometres per second, so for any distance relevant to a nearby thunderstorm (even tens of kilometres), the time for light to reach an observer is negligible and can be treated as effectively zero compared to the several seconds sound takes to cover the same distance.
Does air temperature or humidity change the calculated distance meaningfully?+
Slightly: the speed of sound increases a little with air temperature and, to a smaller extent, with humidity, so the standard constant used is an approximation for typical conditions; the effect is usually small enough to ignore for the practical purpose of estimating storm distance and safety.
Why is this calculation useful for storm safety?+
Tracking the flash-to-bang interval over several consecutive strikes shows whether a storm is approaching (interval shortening) or moving away (interval lengthening), which is directly useful for deciding when to seek shelter, since lightning can strike from a storm cell that's still several kilometres away.