Chicago is facing a dangerous lake-effect snow event overnight Sunday into Monday morning. A narrow, but extremely intense band could dump snow at a rate of 3 or more inches per hour - so fast it overwhelms the ability to keep roads clear.

On Monday, November 9, 2025, more than 80 million Americans across 13 states woke up to dangerous cold weather, with temperatures dropping 10 to 25 degrees below normal for this time of year. The cold air came from the Arctic after something called the polar vortex—a circle of extremely cold air above the North Pole—broke apart and pushed south into the United States.

The forecast calls for cold weather across the central and eastern U.S., with temperatures 10-15 degrees below average, federal forecasters say.

A harsh drop in temperatures is being delivered to the eastern two thirds of the U.S. thanks to a polar vortex dipping down from the Arctic.

RELATED: 4 Regions Where Fall Foliage Will Peak This Month.

The city’s fierce weather pattern is fueled by the same Arctic air mass expected to sweep through the eastern two-thirds of the US this week. Forecasts indicate that today will bring the coldest air to tens of millions east of the Rockies since spring.

The southeastern U.S. has plunged into record-low temperatures, affecting 18 million people under a freeze warning across Alabama, Florida, and Georgia