Dec 23 (Reuters) - A severe winter storm gripping most of the United States threatens to delay millions of last-minute Christmas gift deliveries due to shutdowns at major shipping hubs.

FedEx, United Parcel Service, the U.S. Postal Service and Amazon.com alerted customers that severe weather was disrupting key operations in Tennessee, Indiana, Kentucky, Illinois, the Dakotas and other areas hard-hit by strong winds, bitter cold and blizzards.

Air network shutdowns, road closures and other weather-related disruptions could affect 10-15% of the roughly 75 million daily packages scheduled for delivery on Friday and Saturday, Satish Jindel, founder of consultancy ShipMatrix, told Reuters.

"This is a repeat of what happened in the final two days of Christmas week in 2013," he said.

UPS and FedEx told Reuters they have contingency plans in place if severe weather shuts or idles cargo planes and delivery trucks.

This year's holiday package shipment volumes are down from the record highs set earlier in the COVID-19 pandemic as consumers shift spending back to travel and eating out and as higher food and rental costs bite into disposable income.

As a result, shipping companies have ample capacity to handle this year's holiday delivery surge, Jindel said. (Reporting by Aishwarya Nair in Bengaluru; additional reporting by Lisa Baertlein in Los Angeles; editing by Shailesh Kuber and Sandra Maler)