Weather and greater-than-expected demand caused UPS, the world’s largest package delivery company, to delay a small percentage of packages meant to be delivered by Christmas.

"The volume of air packages in our system exceeded the capacity of our network, as demand was much greater than the forecast," UPS spokeswoman Natalie Godwin told USA Today. "As a result, a small percentage of shipments are delayed and will not be delivered" by Christmas.

UPS drivers delivered packages on Christmas Eve, but not on Christmas Day. Workers at the company's major hub in Louisville, Ky., will work on Wednesday night to sort packages so they can be delivered on Thursday, she said.

The Wall Street Journal reported that UPS estimated its air network would handle about 7.75 million shipments Monday, about 3.5 million of which were expected to be sorted at the Louisville hub. The company declined to say how many packages were affected. Most of the delayed shipments are expected to be delivered Thursday instead.

The hardest-hit area is in North Texas, where the company is still digging out from under the volume of packaged backed up by an ice storm several weeks ago, the Dallas Morning News reported.

“We have had delays and they’ve been much more concentrated in and around the [Dallas-Fort Worth] metroplex than the rest of the country,” said UPS spokeswoman Susan Rosenberg.

UPS pulled its delivery trucks off the road on the night of Dec. 5 through that weekend and “even though the roads were melting, we couldn’t get all of our people back by Dec. 9,” Rosenberg told the Morning News.

Rosenberg said the company has tried to ease the problems by bringing in 900 extra managers to help out at its North Texas distribution centers in Dallas, Fort Worth and Mesquite. The company also has used rental trucks and golf carts to help deliver

UPS delivers upwards of 26 million packages a day during the holiday season, compared with more than 16.3 million on a typical day earlier in the year. The company experienced its peak week last week, when it delivered 132 million packages world-wide at a rate of about 300 packages a second. That included air and ground shipments.

Both the U.S. Postal Service and FedEx said they’re not experiencing many problems.