A major snowstorm in the Midwest and Great Lakes brought winter to some Thanksgiving travelers, and forecasters said the northeast U.S. could get its own early winter storm next week.

Winter storm warnings and advisories extended from Montana to Ohio, the National Weather Service said. Forecasters warned there could be airport delays and slowed traffic with snow falling at more than an inch (2.5 centimeters) per hour in some areas.

The storm dumped more than 8 inches (20 centimeters) of snow on northern Iowa by Saturday morning, and at least that much was expected in Chicago, elsewhere in Illinois, and in Wisconsin, Indiana and Michigan.

Airports in Chicago and St. Louis reported delays of about an hour in the morning, according to FlightAware.com, as one of the busiest travel days cranked up after Thanksgiving.

Icicles formed at a slant on a Chicago pier thanks to the wind, and Lake Michigan’s waters were choppy with whitecaps. Motorists drove cautiously along snowy and slushy roads.

Snow-covered roads and slow travel were reported across Iowa and northern Illinois and Indiana.

Westbound Interstate 70 near Terre Haute, Indiana, was closed around noon after at least 45 vehicles crashed, Indiana State Police said on social media.

No one was seriously injured, and officials estimated that it would take six hours to reopen the highway. Troopers were also helping people in the eastbound lanes who were sliding off the road, Sgt. Matt Ames said.

The sheriff of Grant County, about 65 miles (105 kilometers) northeast of Indianapolis, urged people to stay off the roads.

“Stay home, have a nice cup of hot chocolate, watch some TV, play some games,” Sheriff Del Garcia said in a video.

Snow was falling in Ann Arbor, Michigan, where No. 1 Ohio State played 15th ranked Michigan in their traditional season-ending rivalry game. Heavy snow was expected at other Big Ten games, nighttime contests at Illinois and Michigan State.

Meteorologists said that so far, forecast conditions did not meet blizzard warning criteria — winds of at least 35 mph (56 kph), visibilities of less than a quarter mile (400 meters) and lasting more than three hours.

The same storm and cold front was also expected to bring thunderstorms and a chance of heavy rain Saturday from southern Missouri down to Louisiana and Texas.

Forecasters said another winter storm was becoming more likely Monday and Tuesday, with freezing rain and ice in the Appalachians and moderate to heavy snow possible in the interior Northeast.