Before It Strikes
Before It Strikes
Heat lightning is not a separate kind of lightning and it is not caused by heat. It is ordinary lightning from a thunderstorm far enough away that you cannot hear the thunder, since thunder rarely carries beyond 10 miles while lightning can be seen more than 100 miles away. It is harmless only while the storm stays far away, and storms move.
You are seeing the flash light up distant clouds, often near the horizon, with no thunder. The absence of thunder tells you the distance, not the danger. The same storm is producing normal cloud-to-ground strikes underneath it.
Check which way the storm is moving. A storm you can see on the horizon on a summer evening is usually 30 to 60 miles away, and a fast-moving one can cover that in an hour. If it is coming toward you, plan to be inside before it is within 8 miles. If you cannot tell, a lightning app answers the question directly. How far away is lightning safe?
It is ordinary lightning from a distant storm, harmless only while that storm stays far away. If the storm is moving toward you, it will bring normal lightning with it.
Nothing to do with heat. It is the flash of a thunderstorm too far away for its thunder to be heard, seen on warm nights because that is when distant storms are most common.
Guidance on this page follows the National Weather Service lightning safety toolkit and the Lightning Safety Guide for Sports and Special Events published by CISA and the National Center for Spectator Sports Safety and Security (May 2026). Official NWS warnings always take precedence.
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