Why Today is the Peak Mail Day of 2016

Holiday mail volume at the post office — and the length of the lines — will hit its 2016 peak today as people use the United States Postal Service to send packages or letters in time for the holidays.

When Christmas falls on a Sunday, data shows that the Monday after the last holiday shopping weekend is traditionally the busiest day for mailing things, says USPS senior public relations representative Sue Brennan. The USPS plans to process a total of 611 million packages and letters just today.

If you choose to brave the package pandemonium and head to a post office, you’re hardly alone: the USPS is expecting 5 million people to visit the post offices during the day today, and another 7 million to use the USPS website for the same services.

“I would tell your readers to be very patient if they need to go to a post office today, absolutely,” Brennan tells TIME.

Those who hold off on sending have until tomorrow to ship packages or letters first class if they want them delivered by Christmas (but more expensive options like priority mail will also work later in the week).

The USPS anticipated the year-end spike by hiring 35,000 seasonal staffers. All hands are sure to be on deck this week — the USPS also said peak delivery day will be on Thursday, Dec. 22, when they expect to deliver 30 million packages.