ComEd spokesman Bennie Currie said Friday afternoon that another 13,000 customers were still without power.
That figure includes 6,000 in Chicago, 4,000 in northern Illinois, 1,600 south of Chicago and 900 west of the city.
Currie says he didn't have estimates on when power might be restored.
Rainfall overnight flooded some roads and viaducts. It also boosted the total monthly rain recorded at O'Hare International Airport to 10.45 inches. That makes this July the eighth wettest month ever in Chicago.
The National Weather Service says scattered showers and thunderstorms will move across parts of north-center Illinois Friday. The strongest storms could produce damaging wind gusts and localized flooding.