Temperatures to plunge 25°+ by midweek

This weekend’s summerlike highs around 80º will be distant memories by midweek as the season’s first real autumnal chill blasts into Chicago.
The initial phase of the cool-down will begin Sunday night amid a wave of potentially severe thunderstorms, lowering Monday’s highs into the upper 60s. The real core of the cool air will arrive Tuesday on what promises to a be cloudy and blustery day with light showers and the city’s first sub-60º high since mid-May. Though a modest temperature rebound into the 60s is likely by the end of the week, the autumnal feel will continue with clouds and frequent showers that will add to this month’s substantial rainfall totals.
Eastern Pacific Hurricane Lane made a 120 m.p.h. Category 3 landfall Saturday afternoon on Mexico’s Pacific coast north of Mazatlán. Now weakening, Lane’s remnants threaten flooding and mudslides as it moves north into Mexico’s interior.
-Steve Kahn WGN-TV Meteorologist