Commonwealth Edison says it could take several days to restore power to some of the 100,000 customers still without power following powerful weekend storms as the National Weather Service forecasts a week of a "rather unrelenting" heat wave.

A warm front is expected to move across the Chicago area today and Monday, settling just to the north for much of the week, according to the weather service. Thunderstorms could bring brief breaks in the sweltering weather "but current indications are the heat wave could be rather unrelenting," the weather service said in a statement.