On an average day, the Postal Service says it handles 670 million pieces of mail. On Monday, that figure was expected to jump to about 850 million, or 27 percent more.
That's because many people spend the weekend about 10 days before Christmas addressing cards and gift packages.
The busiest delivery day is expected to be two days later, Wednesday. With Christmas falling on a Thursday this year, next Monday, December 22, is also expected to be busy.
Many post offices will have extended hours through Christmas, so your best bet may be to avoid the middle of the day. Some offices will also be open next Sunday.
If all you need are stamps, consider going somewhere else. According to the agency, more than 82,000 locations will have 2.85 billion stamps. This includes 38,000 Post Offices; more than 21,000 supermarkets, convenience and drugstores; and 16,000 ATMs and 7,000 vending machines located in shopping malls, office parks and airports.
The Postal Service Web site — www.usps.com — will find the outlets nearest you. Click on "Locate A Post Office." Or call toll-free 800-ASK-USPS.
You can also look up ZIP codes online, which will get your mail delivered a little faster. Also make sure that address is readable, and include a copy inside packages just in case something happens to the outer wrapper.
If you are reusing a box or mailing envelope, make sure all previous addresses and bar codes are completely blacked out. Don't use string: It catches in postal sorting machines, and no carrier, not even Federal Express or United Parcel Service, will accept string-wrapped packages.
USPS spokesman Mark Saunders points out that, unlike other delivery services, the Postal Service will deliver on Christmas Day, if you use Express Mail, and often the letter carriers will be dressed in Santa suits.
Your local post office should have a good supply of two types of Christmas stamps: a Madonna and Child stamp from last year, and a new set of four less-religious Holiday Music Makers. There are also Hanukkah and Kwanzaa stamps, plus a flag stamp and something fairly new that might go nicely with your cards — a Snowy Egret bird stamp in rolls of a hundred.