Heres the last day to send your gifts in time for the holidays | Money [Video]

(CNN) — The countdown to Christmas is on, but the threat of delayed packages could dampen the holiday spirit.

Winter storms, out-of-stock items, ground shipping risks and a host of other issues could spell out shipping slowdowns in the days leading up to Christmas Eve.

More than half of Americans say they are worried about deliveries being delayed this holiday season, according to a study in October by Badcredit.org.

“In a shorter holiday season, with only 17 shipping days between Thanksgiving and Christmas, we encourage everyone to ship early and often so you can enjoy the holidays worry-free,” Karen Tomaszewski Hill, US media relations manager at UPS, told CNN.

Companies have also been steeling themselves for a busier-than-usual holiday season. The National Retail Federation confirmed this month that holiday spending could increase by as much as 3.5% from last year and hit a new record of $989 billion.

E-commerce giant Amazon said in …