CHICAGO (CBS) — More thunderstorms were hitting the far northern suburbs Tuesday morning, hours after heavy rain caused significant flooding in the Rockford area Monday evening.

According to the National Weather Service, 3 to 5 inches of rain fell across the Rockford area in less than four hours Monday evening.

Additional rain was moving through Tuesday morning, and heavy downpours could aggravate flooding in some areas.

Flash floods on Tuesday turned roads into rivers in Rockford.

Mark Pickett and Ryan Craig helped rescue an elderly man who was stuck in his car, perched precariously against a railing alongside a swollen creek.

The entire rescue went on for several minutes, and as Pickett and Craig pulled the man out, his car ended up flipping onto its side in the creek.

A witness said the man didn’t want to get out of the car, because he was worried about his wallet.

Rockford firefighters rescued 15 other drivers who were stranded in the flooding.

Multiple homes and businesses also flooded, including the Walmart in Rockford. Store crews frantically tried to whisk out the water with squeegees, as parents used shopping carts as boats to keep kids dry.

The store reopened Tuesday morning after drying out.

The heavy storms also caused a watery scene inside Mercy Hospital in Rockford. One woman who identified herself as a hospital employee took to social media as the water started to pour in.

The National Weather Service reported the lower floors of the hospital took on four to five feet of water. The hospital was evacuated as a precaution, but has since reopened. No patient-occupied areas were affected by the flooding.

A flood warning remained in effect for the Rockford area until noon Tuesday. Many area roads were still covered in water early Tuesday, and might not dry out completely until the late morning. The National Weather Service cautioned motorists not to drive across flooded roads, or risk stalling out.