A period of accumulating snow and dangerous cold will affect much of northern Illinois late Tuesday through early Wednesday, with the National Weather Service warning of hazardous travel conditions during the Wednesday morning commute.

Forecasters say a fast-moving clipper system will arrive Tuesday evening, bringing a narrow but impactful band of snow mainly near and north of Interstate 80. Snow is expected to begin after sunset and continue overnight, with the heaviest accumulation favored closer to the Wisconsin-Illinois state line.

Road conditions are expected to deteriorate late Tuesday night as snow-covered and slick roads develop, particularly across northern counties, including McHenry, Lake, Boone, Winnebago, and Kane.

While snow amounts farther south may be lighter, forecasters are monitoring the potential for a southwest-to-northeast band of snow to develop near and east of the Interstate 55 corridor early Wednesday morning. If that band materializes, travel impacts could extend into the heart of the Wednesday commute across additional counties, according to the National Weather Service.

Conditions may briefly improve on Wednesday afternoon, but another round of winter weather is possible on Wednesday evening as a strong Arctic front moves through the region. Gusty snow showers — and possibly brief snow squalls — could combine with west winds gusting to 35 mph, producing sudden drops in visibility and patchy blowing snow, according to the National Weather Service.

Beyond the snow, bitter cold is expected to settle in late Thursday through early next week. Overnight temperatures are forecast to dip below zero across much of the area, with wind chills potentially reaching 20 to 30 degrees below zero at times. Officials urge residents to prepare for hazardous travel, dress for extreme cold, and stay tuned for forecast updates.