By Aya Elamroussi, Derrick Hinds, Travis Caldwell, Maureen Chowdhury, Aditi Sangal and Tori B. Powell, CNN
From CNN’s Rebekah Riess
The extreme winter weather continues to impede holiday travel plans, as there are more than 1,600 flight cancellations nationwide on Saturday morning, according to the flight tracking site FlightAware.
More than 1,800 flights have also been delayed so far on Saturday.
These airports have been the most affected:
From CNN's Joe Sutton
At least 15 people have died across the United States as the extreme winter weather continues to impact millions of Americans.
Here's a look at details on the deaths:
CNN's Amanda Musa, Caroll Alvarado, Tina Burnside, Raja Razek and Rebekah Riess contributed reporting.
The number of power outages in the US rose dramatically in the last few hours.
More than 1.6 million utility customers were without power as of about 7:50 a.m. ET, according to utility tracker PowerOutage.us. That's up from 840,000 customers at 4 a.m. ET.
The outages at 7:50 a.m. ET included:
Strong winds with gusts of 30-50 mph are forecast for much of the Midwest and Northeast Saturday, which could lead to additional outages.
The loss of power comes as many states are experiencing subzero temperatures, and hazardous road conditions make it difficult for crews to respond quickly.
From CNN's Rebekah Riess and Jason Hanna
Tennessee residents will see intermittent power interruptions Saturday because the frigid weather is putting a strain on the capacity of the state's federally owned electricity provider, utilities in the state said.
The Tennessee Valley Authority, which provides power to more than 150 utilities throughout the state and parts of six surrounding states, told the utilities they must intermittently interrupt electricity service to customers, the utilities said.
The Nashville Electric Service told customers Saturday morning to expect “rotating, intermittent power outages” in about 10-minute increments every 90 minutes to two hours. CDE Lightband, a power company in Clarksville, Tennessee, said power would be interrupted in 15-minute intervals.
Customers should conserve as much energy as possible, CDE Lightband said. The rolling outages are expected to last until the power load is stabilized, the Nashville Electric Service said.
From CNN's Haley Brink
More than 175 million people in the US remain under wind chill alerts Saturday morning, which include both wind chill warnings and advisories.
The wind chill alerts extend from Montana down to Florida, including metro areas such as Minneapolis, St. Louis, Atlanta, Houston and Washington, DC.
The coldest wind chills Saturday morning remain across the Midwest, where temperatures are feeling like minus 20 to minus 30 degrees. Places as far south as Atlanta are experiencing negative wind chills early Saturday.
While wind chill alerts will remain for some areas Christmas morning, they are not expected to be as widespread as Saturday and have been this week. Temperatures are forecast to start rebounding for most areas Sunday through much of next week.
From CNN’s Chris Isidore
If you’re hoping your last-minute Christmas gift will arrive on time, you may be out of luck.
Amazon, the US Postal Service, UPS and FedEx are warning the winter storm hitting large swaths of the United States is disrupting operations in the final delivery days before Christmas.
The US Postal Service said dozens of post offices have been temporarily closed by the storm in South Dakota, North Dakota, Nebraska, Minnesota and Iowa. The agency asked customers to clear snow and ice from sidewalks, stairs and mailboxes to help letter carriers make deliveries.
FedEx told US customers packages expected to be delivered Friday or Saturday could be delayed. UPS said its delays may be somewhat more localized.
Amazon also closed some facilities due to the storm, saying employees at the facilities would be paid for the canceled shifts.
UPS also said air and ground activities are being affected in Louisville, Kentucky, and Rockford, Illinois.
“As a result, some delivery and pickup services in these areas will be affected,” UPS said.
From CNN's Derrick Hinds and Aya Elamroussi
Before daylight Saturday, utility companies were making progress restoring power to homes and businesses, after a strong winter storm knocked out electricity to more than a million customers nationwide Friday.
As of 4 a.m. ET, the number had dropped below 840,000 customers, according to PowerOutage.US.
Four states still have more than 50,000 outages:
Strong winds with gusts of 30-50 mph are forecast for much of the Midwest and Northeast Saturday, which could lead to additional outages.
The loss of power comes as many states are experiencing subzero temperatures, and hazardous road conditions make it difficult for crews to respond quickly.
From CNN's Forrest Brown
It's enough to give anyone already nervous about the chaos in the skies yet another reason to pop an antacid: the prospect of delayed, lost or damaged baggage.
The concern is valid. Especially when an epic winter storm sweeps across the land the week before Christmas. Handing over checked suitcases can almost feel like a leap of faith in circumstances like that.
Scott Keyes, the founder of flight deals and travel advice site Scott's Cheap Flights, said he's encouraging people not to let news of baggage issues put them off their flights and vacations.
"Every bag that gets lost is a huge disruption for the people whose bag that is -- and I certainly don't want to downplay that -- but I do want folks to have the proper perspective that in the vast majority of cases, your flight is going to fly and your checked bag is going to arrive," Keyes told CNN.
Read more about what you can do to help avoid or at least minimize the impact of lost and delayed luggage:
From CNN’s Tina Burnside
Three people have died in weather-related traffic accidents in Kansas, according to police, bringing the number of storm-related deaths nationally to at least 11.
All three fatal crashes occurred in north-central Kansas on Wednesday night, according to Kansas Highway Patrol spokesperson Lt. Candice Breshears.
Deaths from the storm have been recorded by officials in three other states:
CNN's Amanda Musa, Caroll Alvarado, Raja Razek and Rebekah Riess contributed reporting.