It seems counterintuitive but, in its annual orbit of the sun, the Earth actually passes closer to the sun during winter and swings farther from it during the summer. It is a misconception that winter is cold because of greater distance from the sun at that time of the year.
Astronomers refer to the point of Earth’s closest passage to the sun as perihelion, and it occurs today at 9 a.m., when the Earth-sun distance shrinks to 91.3 million miles, or about 3.1 million miles closer to the sun than at aphelion (the point when the Earth is farthest from the sun, in early July). On average, the Earth-sun distance is 93.0 million miles.
Chicago’s winter temperatures average about 45 degrees lower than in summer, and seasonal temperatures are little affected by Earth’s varying distance from the sun. Winter is cold because the Northern Hemisphere tilts away from the sun at that time of the year.
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
