Sun's closer, but can't keep the cold away

It may seem counterintuitive to Chicagoans 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 the greater distance from the
sun this time of the year.
Astronomers refer to the point of the Earth's closest passage to the sun as perihelion,
and it occurs at 9 a.m. Monday when the Earth-sun distance shrinks to 91.3 million miles.
That's 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 the 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.
TUESDAY-WEDNESDAY STORM
The next winter storm arrives at Chicago with snow, potentially heavy, beginning Tuesday
afternoon. Accumulations of at least a few inches are likely before snow diminishes to
flurries late Wednesday.
--By Richard Koeneman, WGN Weather Center Meteorologist