Dangerous Lightning

On average each year, 66 Americans are killed by lightning, and hundreds are injured. Rain or a distant thunderclap often serve as warning signs. But lightning can come completely out of the blue, as in this photo.

Bolts can travel up to 25 miles from cloud to ground, especially on the back side of a thunderstorm when all seems safe.

A "bolt from the blue," as the National Weather Service calls one of these, travels a relatively large distance away from the storm cloud, and then angles down and strikes the ground.

What to do when lightning threatens: Get inside a substantial building. A car is a good second choice. Avoid contact with electrical equipment, plumbing and corded phones. Stay away from windows and doors. Stay inside 30 minutes after the thunder is gone.

—LiveScience Staff

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Credit: Robert A. Prentice, 1990: Robert Prentice's Atmospheric Images