What Is Heat Lightning? Not Real, That's What.

Brian Donegan
Published: August 18,2016
Heat lightning may be one of the most misused weather terms during the summer months, but it is likely not what you think it is.
Many people believe heat lightning is produced by hot and humid conditions, lighting up the night sky without any rain or thunder in the immediate area.

Lightning in northern Idaho
(Emily Sawyers)

This theory is completely false, and heat lightning does not actually exist.
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The flashes of light you are seeing are indeed lightning, but the lightning is from a distant thunderstorm far enough away where the sound of thunder doesn't travel all the way to where you're observing it from.
You can see lightning from a thunderstorm up to 100 miles away, but unless you're within 10 to 15 miles of the storm, you probably won't hear the thunder.
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So-called "heat lightning" can be seen from a thunderstorm that is up to 100 miles away.

The sound of thunder is refracted through the troposphere, or lowest layer of the atmosphere. This is because the movement of sound in the atmosphere depends on the temperature and density of the air, which both change with height. Consequently, the refraction results in sections of the troposphere in which the thunder does not travel through.
Thunder also reflects off the earth's surface, so between the refraction and reflection, there are areas which cannot hear the sound of thunder.
Additionally, since the earth's surface is curved, the thunder may bounce off the earth's surface before it reaches someone viewing the heat lightning from far away.
Although heat lightning is technically not real, it's still exciting to look at, and it's completely safe to do so since the lightning is actually very far away.