The biggest gotcha with a time-based measurement of the thunder is the variability of the speed of sound with temperature - about 0.6 m/s per degree Celsius. Gi

The biggest gotcha with a time-based measurement of the thunder is the variability of the speed of sound with temperature - about 0.6 m/s per degree Celsius. Given that thunderstorms tend to involve pretty significant temperature shifts, the temperature can vary significantly along the path length.