I know a man-made land feature like a highway can’t affect the weather. What conditions lead to the boundaries of fronts seemingly setting up along something like Interstate 80, or do you just use them as a handy reference?
— J. Wadsworth, Oak Park
Chicago forecasts often use well-known map features like highways to describe where weather is expected to occur because they do provide easy references. Thunderstorms first reach the I-39 corridor as they approach the Chicago area, or the snow shield from a winter storm will affect only portions of the area south of I-80. East-west frontal boundaries often stall out along the I-80 corridor — not because of the interstate but because the highway coincides with the southern end of Lake Michigan, a feature that does affect the weather.