Dear Tom,
On average, how many days a year does Chicago experience fog?
Alice H.
Dear Alice,
On many cool, calm mornings around sunrise, parts of the Chicago area, especially in the suburbs, will experience ground fog as the air cools to saturation. The fog usually burns off quickly, creating only brief inconvenience. There are many other days where light fog is present from a variety of causes resulting in reduced visibility. However, there are only an average of about 12 days each year when Chicago is socked in with dense fog (visibility one-quarter mile or less) that seriously impacts transportation. Dense fog is most common here during the cold season, frequently occurring when warm, moist air passes over cold snow-covered ground. December through March hosts a majority of the area's dense fog occurrences with each month averaging about two days.
On average, how many days a year does Chicago experience fog?
Alice H.
Dear Alice,
On many cool, calm mornings around sunrise, parts of the Chicago area, especially in the suburbs, will experience ground fog as the air cools to saturation. The fog usually burns off quickly, creating only brief inconvenience. There are many other days where light fog is present from a variety of causes resulting in reduced visibility. However, there are only an average of about 12 days each year when Chicago is socked in with dense fog (visibility one-quarter mile or less) that seriously impacts transportation. Dense fog is most common here during the cold season, frequently occurring when warm, moist air passes over cold snow-covered ground. December through March hosts a majority of the area's dense fog occurrences with each month averaging about two days.
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