AUSTIN, Texas (AP) — Airlines canceled hundreds of flights Tuesday, governors urged residents to stay off roads and schools closed campuses as a huge swath of the U.S. braced for a major winter storm that was set to put millions of Americans in the path of heavy snow and freezing rain.

The approaching blast of frigid weather, which was expected to begin arriving Tuesday night, put a long stretch of states from New Mexico to Vermont under winter storm warnings and watches. More than a foot of snow was possible in southern Michigan, on the heels of a vicious nor’easter last weekend that brought blizzard conditions to many parts of the East Coast.

“It will be a very messy system and will make travel very difficult,” said Marty Rausch, a meteorologist with the National Weather Service in College Park, Maryland.

While it will be cold today and Thursday, the storm is expected to stay well south of the Upper Peninsula and northern Wisconsin.

The projected footprint extends as far south as Texas, where nearly a year after a catastrophic freeze buckled the state’s power grid in one of the worst blackouts in U.S. history, Gov. Greg Abbott defended the state’s readiness. The forecast does not call for the same prolonged and frigid temperatures as the February 2021 storm and the National Weather Service said the approaching system would, generally, not be as bad this time for Texas.

Abbott said thousands of miles of roads in Texas will become “extraordinarily dangerous” over the coming days.

Airlines canceled more than 1,000 flights in the U.S. scheduled for today, the flight tracking service FlightAware.com showed, including more than half taken off the board in St. Louis. Missouri Gov. Mike Parson declared a state of emergency as school districts and universities shifted classes to online or canceled them entirely.

Chicago O’Hare International Airport also canceled more than 100 departing flights, and airports in Kansas City and Detroit were also canceling more flights than usual.

Illinois lawmakers canceled their three scheduled days of session this week as the central part of the state prepares for heavy snow, ice and high wind gusts.

The National Weather Service said 6 to 12 inches of snow was expected by Thursday morning in parts of the Rockies and Midwest, while heavy ice is likely from Texas through the Ohio Valley.

Today and Thursday, the weather service said 8 to 14 inches of snow was possible in parts of Michigan. That includes Detroit, where the mayor activated snow emergency routes and city crews were expected to work 12-hour shifts salting and plowing major roads.

In Tulsa, Oklahoma, where up to 7 inches of snow and sleet are forecast but little ice, emergency management director Joe Kralicek said the event is not expected to cause large-scale power outages based on an ice index used by the National Weather Service.

Becky Gligo, director of the nonprofit Housing Solutions in Tulsa said teams are working to move homeless people into shelters.