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Arctic air: A type of air mass whose characteristics are developed in the cold season over ice- and snow-covered areas of the far north. It has low temperatures, low moisture content, and is very stable. It covers Chicago about 6 percent of the time.
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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.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
