The U.S. National Weather Service (NWS) warned Thursday that a major and unusual storm system affecting nearly two-thirds of the United States is forecast to produce of “a multitude” of winter weather hazards over the next three days, including heavy snow, strong winds and dangerously cold temperatures.

In its latest advisory, the NWS said the powerful winter storm could produce widespread disruption and “potentially crippling impacts” across the central and eastern United States.

By Friday, about 75% of the country is projected to have freezing temperatures with wind chills below zero as far south as the southeastern U.S. state of Georgia.

The weather service reports temperatures behind the weather front have plummeted by as much as 18 degrees Celsius (50 degrees Fahrenheit) in just a few hours. Current winds of 30 to 50 kilometers per hour could rise as high as 100 kilometers per hour, creating wind chills as cold as minus 45 Celsius.

The forecasters said temperatures that low can cause frostbite to exposed skin in less than five minutes and hypothermia and death with prolonged exposure.

From the White House Thursday, U.S. President Joe Biden warned of the dangerous storm, saying, “This is really very serious weather alert here. … And it’s of real consequence.” Biden encouraged everyone to heed any local warnings.

The storm comes amid one of the busiest travel times of the year, just days before the Christmas holiday.

Early Thursday, Chicago’s O’Hare International Airport, one of the nation’s busiest travel hubs, reported more than 400 hundred flights had already been canceled.