Several states in the Midwest and Northeast will be affected by severe snowstorms on Thanksgiving Day, according to forecasts by the National Oceanic and Atmospheric Administration (NOAA) and the National Weather Service.

The snowstorms, the result of an Arctic swell that will hit the United States from Canada, will be in Washington, Idaho, North Dakota, South Dakota, Minnesota, Wisconsin, the Upper Peninsula of Michigan, Pennsylvania, and Western New York. Minnesota will be hit hardest, with at least six inches of snow and wind speeds of 45 miles per hour forecast for the Twin Cities region of Minneapolis and St. Paul, where the temperature with wind chill on Thanksgiving Day will be just 12 degrees Fahrenheit.

“A strong storm system will cross from the north-central U.S. into the Great Lakes and Northeast by Thursday, producing areas of snow, rain, and gusty winds. Additionally, unsettled weather will impact the Pacific Northwest,” wrote the National Weather Service on social media.

“Thanksgiving forecast: Wet and wintry weather cause widespread travel troubles,” wrote the NOAA on social media. “Colder air is preparing to rush into the Lower 48 just in time for Thanksgiving Day festivities across the country.”

The rest of the country is unlikely to be affected beyond colder weather and some precipitation, mostly as rainfall. Cities in the South will have lower than usual temperatures, with 50 degrees in Houston; 33 in Jacksonville, Fla.; 28 in Atlanta; and 24 in Washington. The center of the snowstorm will be Michigan and Northern Wisconsin, where up to 30 inches of snow may fall.

The rough weather, coupled with the high volume of domestic travel around Thanksgiving, means travelers could face delays and cancellations. Flight and train reservations are expected to be affected, while other travel-related amenities, such as rental cars and hotels, may be fully booked in many major cities.

“We expect this Thanksgiving holiday travel period to be the busiest in 15 years, with Tuesday, Nov. 25 being the peak travel day with more than 52,000 flights,” wrote the Federal Aviation Administration on social media.

Transportation Secretary Sean Duffy urged travelers to be patient and courteous.

“You have brawls at baggage claim, you have passengers berating gate agents,” lamented Duffy in televised comments on Nov. 23. “We have unruly passengers on airplanes. People dress up like they’re going to bed when they fly.”

On the subject of dress, Duffy also advised travelers “not to wear slippers and pajamas as we come to the airport,” targeting an increasingly common practice, as part of his recently launched civility campaign titled “The Golden Age of Travel Starts with You.”