Sunday night, at least four large city blocks were under water, and as many as 1,000 homes had been evacuated.
It is the worst flooding Munster has seen in years. The Indiana National Guard was called in to assist in the emergency effort.
Earlier in the day, the parking lot of a Munster strip mall off of Calumet Avenue was almost entirely under water, and the scene was replicated on several nearby streets in residential neighborhoods.
The floods left authorities scrambling to get waterlogged residents to safety. Some families had to be rescued by boat.
"We're waiting for the boat to come and get us. As we're standing there, the waters was about to come in the front door," said evacuee Kathie Bednarowski.
"My crawlspace is flooded. It's coming up. I want to get my kids out of here so they can be safe," evacuee LaShandra Robinson said.
Officials say the biggest problem is the Little Calumet River. It crested Sunday evening at just over 17 feet, which is 5 feet above flood stage.
During the day Sunday, dozens of volunteers were sandbagging at a public works garage to try to keep up with the water, but it was too late to stop full breaches that happened in certain spots.
The town of Munster has issued an evacuation order for parts of the city near the river.
"We're insisting that residents leave the area immediately if they haven't already. It's a dangerous situation. Anyone who stays in their home, we can't guarantee their safety," said Mike Mellon of the Munster Town Council.
Also evacuated was a nursing home where the basement was already flooded. Authorities were worried about possible power outages.
Anyone trying to flee flooded areas by way of the Bishop Ford expressway could have trouble. The expressway is closed southbound to Interstate 80, and northbound between 130th Street and 147th Street. Drivers are urged to take the Skyway instead.
The Borman is also shut down from Calumet to Klein Avenue in northwest Indiana in both directions.
The Illinois Department of Transportation has also closed eastbound Interstate 80/94 at Route 394 until the Borman reopens. The closure backed traffic up for miles Sunday.