A 57-degree reading recorded at 10:59 a.m. Friday proved all the atmosphere here could
muster. It was the second consecutive day readings failed to reach 60 degrees -- the first
time that's happened in nearly five months. Rain falling into a dry layer of air and
evaporating Friday afternoon -- a process meteorologists refer to as "evaporative cooling"
-- sent temperatures falling to late-November levels. By mid-afternoon, readings had
retreated to the mid-40s in Wheaton, Naperville, Darien and Frankfort -- easily the
coolest since May 27. Friday's chill followed a night of 30s in many suburban areas --
with cool air responsible for frost at some locations. Clouds eventually break Saturday --
but Sunday appears to be this weekend's real winner as gusty south winds bring a
temperature surge to Chicago. Though a far cry from last Sunday's record 84 degrees at
O'Hare Airport, Sunday's 70-degree high will be a 12-degree improvement over Saturday's
58. A system taking shape later next week threatens wetter weather. And at least four
punches of cool air are possible in October's remaining days. Despite recent chills,
October to date here is more than 2 degrees above normal -- but is running 4.8 degrees
behind a year ago.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
