Weather Library > Lightning FAQ: Sometimes I've seen a bright blue-green glow coming from the ground right after a lightning strike. What causes this?

By DAN ROBINSON
Editor/Photographer

It is not uncommon for lightning to strike electrical power equipment (power lines, transformers, etc.). When this happens, many times the lightning will cause a secondary arc. These arcs are usually referred to as power flashes. These power flashes are extremely bright and can easily light up the night sky. They can flicker like lightning, or glow for a second or two before the circuit breakers trip and turn off power to the line (see video clip below).

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Video clip of lightning-triggered flashover
Windows Media, 157KB

To see a more detailed description on how lightning causes electrical arcs or flashovers see our article about flashovers.

See Also:

		Flashovers and Strikes to Power Lines A commonly seen, but frequently misidentified phenomenon observed when lightning strikes an energized power line.

		Power arcs caused by storm events The 'real story' behind the flashes mistakenly called 'exploding transformers'.

		FAQ: What color is lightning?