BUFFALO, N.Y. (AP) — Dangerously cold wind chills continued to affect much of the Rockies, Great Plains and Midwest on Tuesday, with wind chills below minus 30 degrees (minus 34.4 C) in many parts of the central U.S.

About 110,000 U.S. homes and businesses were without power late Monday, the bulk of them in Oregon after widespread outages that started Saturday. Portland General Electric warned that the threat of freezing rain Tuesday could delay restoration efforts. Transportation officials urged residents to avoid travel as roads were expected to be hazardously slick with ice that could weigh down trees and power lines, causing them to fall.

Classes were canceled Tuesday for students in Portland and other major cities including Chicago — home to the nation’s fourth-largest public school district — Denver, Dallas and Fort Worth.

The storms and frigid temperatures were affecting everything from air travel to NFL playoffs games to Iowa’s presidential caucuses, and were also the cause of several deaths around the country.

At least four people in the Portland area died, including two people from suspected hypothermia. Another man was killed after a tree fell on his house and a woman died in a fire that spread from an open-flame stove after a tree fell onto an RV.

In Wisconsin, the deaths of three homeless people in the Milwaukee area were under investigation, with hypothermia the likely cause, officials said.

Freezing rain and sleet was expected continue across portions of the Southeast into Tuesday morning. Winter storm warnings were in effect for Lawrence, Limestone and Madison counties in Alabama and in Franklin County in Tennessee, southeast Arkansas, northeast Louisiana and much of northern, central and southwestern Mississippi.

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Monday night saw temperatures drop as low as 10 degrees (minus 12.2 C) in Olive Branch, Mississippi, and Jackson, Tennessee.

Frigid temperatures in the Northeast didn’t stop fans from heading out to cheer on the Buffalo Bills at a snow covered Highmark Stadium in Orchard Park, New York. The Bills beat the Pittsburgh Steelers on Monday in an AFC wild-card playoff game that was delayed 27 1/2 hours because of a storm that dumped more than 2 feet (61 centimeters) of snow on the region.

And voters handed former President Donald Trump a win Monday night in the coldest first-in-the-nation Iowa caucuses on record. Temperatures dipped to minus 3 degrees (minus 19.4 C) in Des Moines, with the wind chill making it feel far colder.

Air travelers across the country experienced delays and cancellations. The flight tracking service FlightAware reported about 2,900 cancellations Monday within, into or out of the United States.

Temperatures are expected to moderate midweek but a new surge of colder air is forecast to drop south over the Northern Plains and Midwest, reaching the Deep South by the end of the week.