New York — Hanukkah and Christmas are less than a week away and it's crunch time for holiday deliveries. But some major shipping companies are struggling to deliver packages on time.

FedEx, UPS, and other delivery services are expected to deliver more than two billion packages this holiday season. Overall shipping volume is up more than 21% this year. But all that cargo, coupled with recent storms, has delayed on-time deliveries.

Since Thanksgiving, FedEx has an on-time delivery rate of about 68%, down from more than 77% a year ago. For UPS, it's 80%, down from 86% this time last year.

"They are certainly getting inundated with the volume. They are doing everything they can by expanding their networks but the reality is there will be just a little less time to get it all done this year," said Chris Wetherbee, a senior transportation analyst with Citi.

Black Friday and Cyber Monday happened later this year, leaving fewer days before the Christmas deadline. With the holiday just days away, those who order at the last minute risk a repeat, paying the ultimate price of a late delivery.

"You'll still be able to get things but you're likely going to have to pay for it and it's going to be by air which is the most expensive products they offer," Wetherbee said.