UPS backlog means missing gifts under Christmas tree for some December 25, 2013 -- Updated 0839 GMT (1639 HKT) UPS put out a message saying some packages may be delayed The company said some could arrive after Christmas They blamed the delays on high demand (CNN) -- Santa wasn't the only one racing against the clock to get packages to homes last night. UPS was too. But some of you may find a few gifts missing under the Christmas tree this morning. Two factors conspired, the company said: high demand and bad weather. "The volume of air packages in our system exceeded the capacity of our network as demand was much greater than the forecast, resulting in some shipments being delayed," UPS said in a tweet Tuesday night. We expect a vast majority of these packages will be delivered the day after Christmas. The day after Christmas? That hasn't made for a silent night at the customer service department at UPS. Susan Rosenberg, a company spokeswoman, said the Dallas area is seeing its share of frustrated customers. She attributed the backlog to the ice storm that hit in mid-December and an influx off online shoppers. She said the company is employing an "all-hands on deck" to get deliveries out. But the delays were a problem in several cities coast to coast. Julie Strachan of San Francisco was one of many waiting for a present to arrive on Christmas Eve. I was expecting my husband's big Christmas gift at my office and today is the last day before Christmas. So I waited around for hours and hoping for it to show up and it never did," she told CNN affiliate KGO on Tuesday. Strachan went to a UPS center in San Francisco to wait. Hours later, she left empty handed. "I definitely paid a little bit more to expedite the shipment for Christmas, so (it's) a little disappointing," she said. UPS has said it planned to make more than 120 million deliveries this week, its busiest of the year. "We apologize for the delay," Natalie Godwin, another company spokeswoman, said earlier this week. But we can't control the weather. CNN's Janet DiGiacomo contributed to this report.