Rain Pattern in Chicago, IL
Name: Jennifer Mundt L.
Date: Tuesday, April 23, 2002
Why does Chicago have more rain in the spring than in the
Most of the rain in the Chicago area in the spring and summer comes from
moisture that is carried north from the Gulf of Mexico, and falls in the
form of showers and thunderstorms.
The storm systems that produce the rain from the moisture brought north
are more frequent in the spring than in the summer. Also, slightly less
moisture is brought north during the summer, and the showers and
thunderstorms are more isolated.
Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO
During Spring there is a greater gradient of temperature from north
to south than there is in summer. There are still cold, dry air
masses coming down from Canada and warm, humid air coming north
from the southern part of the United States. At the boundary of
these very different temperature and humidity regimes you get a
lot of convection, (rising air), which transforms into strong
cold fronts (with embedded thunderstorms), squall lines (made
up of thunderstorms), and even isolated thunderstorms. These
provide a lot of rain. In the summer, temperatures don't
change from north to south as much and strong weather systems
can't develop as easily or frequently, giving us less rain
in the summer.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
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Update: June 2012