Books close on warmest October in 36 years
Chicagoans haven’t experienced an October milder than the one just completed in 36 years—since 1971. The month finished with an average temperature of 60.4° at Midway Airport—a reading well above the 54.1° October average since 1928. Only four Octobers have been milder there in the past 80 years.
This autumn’s mild, dry character is typical of a Niña autumn. La Niñas are declared when ocean temps in the central equatorial Pacific drop 0.5° or more below normal over three consecutive months, a shift which produces weather changes globally. Among them is the tendency for autumns to be mild and dry over a huge swath of the country. Winters can be a different story. La Niña winters have been known to turn wetter in the Midwest, roughly from Chicago south. And, while temps in these winters often average above normal, La Niña winters can be volatile—featuring spells of bitter cold interspersed with spells of mild Pacific air.
--By Tom Skilling, WGN-TV Chief Meteorologist