Dear Tom,
This morning my parents and I saw a rainbow in the west. I thought they only occurred in the east.
Ashley Salamone
Dear Ashley,
Rainbows form when sunlight passes through raindrops and separates into the colors of the spectrum. They are always visible in the portion of the sky opposite the sun. The viewer of the rainbow is actually seeing a combination of reflection and refraction of different colors of light from each raindrop that combine to form the rainbow’s distinct color bands.
The untrue statement that a rainbow is only visible in the east is based upon the premise that most showers occur in the afternoon when the sun is headed for the western horizon. If rain is falling in the morning while the sun is rising through the eastern sky, any observed rainbow will be visible opposite the sun in the west.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
