Dear Tom,
Does a 60 percent chance of rain mean 60% coverage over the rain area, or that it will rain six times out of ten?
Robert Crane, Riverwoods, Ill.
Dear Robert,
The proper interpretation of a 60 percent chance of rain (assuming the forecasts verify perfectly) is that you will have rain on your head six out of ten times that you hear such a forecast.
The forecaster may believe rain will cover 100% of the area if the rain arrives, but his confidence that it will arrive is only 60%. Alternatively, the forecaster might have great confidence that rain will occur, but he believes it will be showers affecting only 60% of the area.
Regardless of the forecaster’s intent, the meaning for you is always the same: The chance of rain on your head is 60%.
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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.
