Map Shows States Facing 'Notoriously Unpredictable' Ice Jams

Six states are at risk for "notoriously unpredictable" ice jams as excessive rainfall prompts melting, shifting ice that can quickly overwhelm riverbanks with floodwaters.

Flood warnings have been issued in numerous states this week as torrential rain pummels the U.S. Extreme floods wreaked havoc in San Diego earlier this week. One city in Central Texas received nearly 12 inches of rain in 72 hours. In the Midwest and Northeast, excessive rainfall resulted in ice jams.

The National Weather Service (NWS) issued a flood watch for Indiana, Ohio, Illinois, West Virginia, New York and Michigan warning residents in those areas to be alert for flooding caused by ice jams. Typically, ice jams form in the spring as the ice thaws and then begins to move. The chunks become stuck in piles near bridges or river bends, which causes the river to flood.

However, NWS Chicago Senior Service Hydrologist Scott Lincoln told Newsweek that ice jams can occur in the winter too, although it's not as common for an ice jam to be so severe that it causes water to overwhelm the river's banks like it is currently. Lincoln said some of the contributing factors for the ice jams in Illinois are the recent arctic blast that plunged the region into subzero temperatures.

The NWS alert in Illinois cited that a "combination of rain, snowmelt, and heavy river ice" could result in flooding.

"Ongoing ice jams may break, causing rapid-onset flooding of areas downstream," the warning said.

When coupled with additional rainfall, the ice jams will cause "strong rises" on creeks and streams.

"Water levels around ice jams are notoriously unpredictable, and can change quickly with little or no warning. Anyone living or recreating near the river should pay close attention over the next few days and prepare for additional changes in water levels," the alert said.

Several photos of the phenomenon have been shared across social media in the past week.

Conditions were improving in Illinois after ice jams formed near Bardwell Island.

"A large portion of the river remains covered with solid ice," the Will County Emergency Management Agency posted on X, formerly Twitter, on Monday with pictures of the ice jams.

Multiple rivers in Illinois were impacted last week, as well.

"We are continuing to monitor the ice jams that have developed on the Kankakee River and the Illinois River," the Illinois Department of Transportation posted on January 17 with a photo of an ice jam. "As the weather shifts, flooding can impact roadways, yards, and parks along the river, as well as damage to structures along the river by shifting ice."