(CNN) An arctic blast that killed at least 23 people in the United States should ease over the weekend, replaced by erratic temperatures that will melt snow and ice and cause more problems.

This week's deep freeze grounded thousands of flights and halted dozens of trains in the Midwest. Officials in some of the hardest-hit cities, such as Minneapolis, Detroit and Chicago, implored residents to stay indoors to prevent frostbite and to keep motorists off icy roads.

With the biting cold moving out, temperatures will be all over the place in the next few days, a rapid change that will cause thermal whiplash for people living in affected areas.

"Get ready for some serious ups and downs in the world of temperatures. The Twin Cities will go from around negative 25 this morning to around 45 above on Sunday back to around negative 10 by next Wednesday night," the National Weather Service tweeted Thursday, referring to Minneapolis and St. Paul.

That will be about 125 degrees in temperature change over seven days, it said.

13 million people are under wind chill alerts

Forecasters describe wildly fluctuating weather trends as whiplash.

At the cold's peak Thursday, more than 216 million people experienced temperatures below freezing. By Friday morning, about 13 million were under wind chill warnings or advisories.

Chicago's temperatures will skyrocket in the next few days -- from a low of minus 23 degrees Fahrenheit on Wednesday to the 50s Monday -- a change of more than 70 degrees, CNN meteorologist Haley Brink said. Atlanta shivered in the 20s this week but will bask in the 60s when it hosts the Super Bowl on Sunday.

In Detroit, the metro airport had 36 hours of below-zero temperatures through Thursday, its longest such streak since January 1994. The city's temperatures will be in the 30s Saturday, 40s Sunday and into the 50s Monday, the National Weather Service tweeted.

Despite higher weekend temperatures, some weather-related headaches lingered for travelers. More than 450 flights involving US airports were canceled Friday -- down from 2,300 the previous day. The majority of them were due to fly out of Chicago, according to flight-tracking site FlightAware.com

Chicago's L trains move along snow-covered tracks Monday.

Flooding is possible during the thaw

Despite the prospects of higher temperatures, light snow fell in the area Thursday night, leading to slippery roads and slower commutes. Before the weekend warms up, more snow will hit parts of Illinois, Indiana and Ohio, the weather service said.

When Chicago's above-freezing temperatures start Saturday, snow and ice will melt, and that could cause flooding along rivers as large pieces of ice break and jam the flow of water downstream, Brink said. Other hazards include the falling of icicles that have formed on buildings.

"Chicago's average high is 32 degrees Fahrenheit for this time of year," Brink said. "They are going from well below average temperature to well above average temperatures."

Ice covers the Lake Michigan shoreline this week in Chicago.

11 states had temperatures lower than Alaska city

The brutally cold weather was so intense Thursday, at least 11 states in the continental United States hit a temperature lower than the one recorded in Alaska's northernmost city.

The Dakotas, Minnesota, Illinois, Iowa, Indiana, Michigan, New Hampshire, Wisconsin, New York and Pennsylvania all saw temperatures fall below minus 14 degrees, according to CNN meteorologist Taylor Ward. That was the temperature in Utqiagvik (also known as Barrow), a town of about 4,400 that sits north of the Arctic Circle.

At least 50 people were treated for frostbite in Chicago, a majority of them homeless. Under such extreme conditions, frostbite can set in as quickly as three to 10 minutes, depending on age, exposure and other factors such as wet gloves and socks.

The bone-chilling weather also caused a phenomenon called cryoseism in Chicago -- loud booms referred to as a "frost quake." It happens when water underground freezes and expands, causing soil and rock to crack.

Of the 23 deaths linked to this week's extreme weather, three were in New York's Erie County and two in Chicago. They included someone found dead at a bus stop, and two men who were removing snow, said Peter Anderson, spokesman for the Erie County executive's office.

In Chicago, a 92-year-old man's death was brought on by cold exposure, according to the Cook County Medical Examiner.