Debunking The Myth Of Heat Lightning

There are many, many weather myths…nuggets of “wisdom” that have been passed down from generation to generation. Many people hold on to these tightly; their dad or grandma or great aunt insisted these things were true! Believe me, I understand. My grandmother was largely responsible for getting me interested in weather and many of her weather-related anecdotes and pearls of wisdom, as it turns out, were not exactly filled with scientific rigor. And that’s ok! Some weather myths are harmless fun and others (such as a few related to tornado safety) can actually be dangerous.

At this time of the year, one of the most common weather myths that gets some play is “heat lightning”. This is a term that many people associate with warm summer evenings in which you can see lightning in the distance but don’t hear any associated thunder. Often the sky directly overhead is clear. The general idea behind heat lightning is that, well, it’s really warm and sometimes that just makes lightning form. I guess?

Well the truth is, lightning is lightning and it all forms by the same processes.  An electric charge is formed in a tall cloud by chunks of ice (some big, some tiny) bumping into and rubbing against each other.  When the charge grows large enough, a giant spark-lightning- occurs between positive and negative charges.  That discharge can occur within a cloud, from cloud-to-cloud or from the cloud and the ground.


All lightning produces thunder, it’s just that sometime we can’t hear it. Lightning can be seen from as much as 100 miles away. But thunder can usually only be heard from a distance of about 10 miles away.

The curvature of the earth plays a role. A distant thunderhead may be mainly below the horizon from your vantage point. But the lightning at the top of the storm may still be seen.

Finally, don’t forget: every time someone spells lightning “LIGHTENING”, a meteorologist’s blood pressure ticks upward.