What is Heat Lightning … and Is It Dangerous?

Ever seen flashes in the sky on a hot day you can't quite explain? You might be witnessing what some people call "heat lightning."

Have you ever been outside on a hot summer day and seen flashes of light bounce along the horizon without hearing any rumbles of thunder? Many people believe these flashes are a phenomenon known as “heat lightning,” where the heat in the upper atmosphere creates sparks of light that silently illuminate the sky.

But what actually is “heat lightning?” And is it dangerous?

What is Heat Lightning?

Turns out, what some people call heat lightning is just lightning from a far-off storm.

According to the Weather Channel, the human eye can see lightning up to 100 miles away, but the human ear can only hear thunder if it’s within 10 to 15 miles of the storm. Because people can’t hear the thunder, they see the distant lightning and assume it’s some sort of rare natural phenomenon.

And because summer storms tend to hit on notably hot days, some draw a false correlation between this “special” kind of lightning and the heat. Thus, the common myth of “heat lightning.” In reality, lightning and heat lightning are exactly the same thing. It’s just a matter of perspective.

Is Heat Lightning Dangerous?

Heat lightning is actually much less dangerous than regular lightning, simply because it is so far away. According to the National Weather Service, lightning can travel up to 12 miles from the thunderstorm generating it. That means that if you can hear thunder, it’s possible that you could get hit by lightning.

But the inverse is also true. If a lightning storm is far enough away that it looks like “heat lightning” and you can’t hear its thunder, you and your surrounding area should be safe from any wayward lightning strikes. So go ahead and spend some time watching your next “heat lightning” storm. Even if heat lightning might not be technically real, it’s still a fairly rare event— and pretty cool to look at.

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