CHICAGO (AP) — As winter made an early entrance, large regions across the U.S. braced for the season’s initial cold snap on Sunday. The Northern Plains experienced a drop in temperature with snowflakes swirling, while snowstorms moved eastward over the Great Lakes, and the South anticipated a significant drop in temperatures.

In Chicago, snowflakes began to dust the area on Sunday, signaling the onset of “intense” snowfall expected to hit Lake Michigan’s neighboring regions by evening. The National Weather Service announced a winter storm warning extending into Monday, forecasting wind gusts reaching 30 mph (48 kph) and predicting up to 18 inches (46 centimeters) of rapid snowfall, accompanied by thundersnow, a phenomenon where thunderstorms occur with snowfall.

“This band is going to drop some very heavy snow and some hairy scenarios for the Monday morning commute,” remarked Kevin Doom, a meteorologist with the weather service in Romeoville, Illinois.

Weather experts cautioned that road conditions in northeast Illinois might become “dangerous to impossible” due to snow accumulating at rates exceeding 3 inches (8 centimeters) per hour.

With temperatures plunging across the central U.S., meteorologists issued winter weather advisories highlighting hazardous travel conditions for Michigan, Indiana, and Wisconsin. Snow descended on Michigan’s Upper Peninsula on Sunday, where experts warned of reduced visibility with up to a foot expected by Monday. In Indiana, forecasts called for up to 11 inches (28 centimeters) of snow and roads becoming “slippery.” Parts of Wisconsin could see up to 6 inches (15 centimeters) of snow.

In areas of Minnesota, Nebraska, and South Dakota, “patchy blowing snow” and wind chills nearing zero were anticipated. Some regions had already received measurable snowfall the previous day, with southwest Minnesota recording 4 inches (10 centimeters) and northern Iowa seeing more than 5 inches (13 centimeters).

Cold weather warnings were issued for Ohio, West Virginia and Kentucky, with freezing temperatures predicted through Monday morning for a large swath of the South, from Texas and Oklahoma to Alabama and Georgia.

Weather experts issued special guidance for gardeners, saying the freeze warning means the growing season has ended.

“Take steps now to protect tender plants from the cold,” warned meteorologists in Arkansas.