CHICAGO >> Showers and thunderstorms dumped heavy rainfall across the Chicago area, swamping streets with floodwaters that knocked out power overnight to the 110-story Willis Tower after the storms spawned two possible tornadoes, the National Weather Service said.

Weather spotters reported that one tornado touched down Sunday evening south of Sandwich in far northeast LaSalle County, and a second struck near Braidwood, along the Grundy County and Will County line, the weather service in Chicago said. Forecasters said no damage was reported from either storm.

The weather service in Lincoln said another tornado briefly touched down Sunday afternoon in central Illinois, and was intermittently on the ground as it moved through the Macon area, damaging some trees.

Sunday’s unrelenting rainfall sent floodwaters coursing into the Willis Tower’s basement, affecting a ComEd substation and cutting power to the skyscraper. Flooding also halted CTA trains and made many roads impassable, including Lower Wacker Drive, prompting fire crews in rafts to rescue at least half a dozen people.

In the suburban Chicago community of Lyons, where the water was chest deep on some streets, the fire chief said boats had to be dispatched to rescue about 40 people — and their pets — from their homes.

Gordon Nord, the fire chief in the western suburb, told NBC 5 in Chicago that he thought it would be a few days before the water recedes enough to allow people back into their homes.

A flood warning issued by the weather service remains in effect across the Chicago area and much of northeastern Illinois and parts of northwestern Indiana until early this afternoon.