Brutal cold that can cause frostbite within a few minutes blasted the Midwest for a second day and blew into the Northeast on Thursday, snarling air traffic and delaying Amazon and other package deliveries.
Amazon said it closed some buildings, including fulfillment centers across the Midwest that were affected by the numbing low temperatures.
"We work hard to deliver on our fast, free shipping promise, but weather conditions are out of our control," Amazon said in a statement. "Customer service is available to work with any customer who is experiencing an issue."
United Parcel Service said it had suspended package deliveries and pickups in parts of upstate New York and across a wide swath of the Midwest for safety reasons as temperatures remained low and federal forecasters warned of "dangerously low wind chill values." UPS listed affected areas by ZIP codes in the Midwest and New York on its website.
Rival FedEx closed some of its offices early, including in Chicago and Detroit, scaled back service in cities across the Midwest, saying: "Our priority is always safety and providing service to the best of our ability."
The U.S. Postal Service suspended deliveries in some cities in the Midwest on Thursday "to ensure the safety and well-being of our employees."
The stinging cold hobbled Chicago's main airports on Thursday, as it was too cold for ground workers to access and service many aircraft.
Airlines canceled more than 1,400 flights on Thursday at Chicago's O'Hare International Airport, more than half of the daily schedule at the United Airlines and American Airlines hub. More than 40 percent of the schedule, or 237 flights at Chicago Midway International Airport, were canceled, according to flight-tracking site FlightAware. Hundreds of other flights were canceled in Chicago on Wednesday due to the cold.
Temperatures at O'Hare at 5:30 a.m. were minus 21 degrees, with wind chills of 37 degrees below zero, the National Weather Service said.
Delta Air Lines, American, United, Spirit Airlines and JetBlue Airways said they would waive date-change fees for travelers affected by the severe weather. Southwest Airlines, which doesn't have date-change fees, said it wouldn't charge travelers booked in and out of more than two dozen U.S. airports the fare difference to fly at a later date due to the extreme weather. Southwest canceled 410 flights on Thursday, about 10 percent of its schedule.
While aircraft can take generally take off in low temperatures, the bitter cold limits how long ground workers can remain loading baggage or provide fuel and other essential services for aircraft.
Delta, which operates hubs in Minneapolis and Detroit, prepared for the frigid conditions by increasing staffing of ground workers. Employees can take more frequent breaks indoors, as the airline can prepare for the low temperatures by moving some aircraft into heated hangars overnight, said spokesman Michael Thomas.