MID-WINTER, after Christmas, is a time for stock taking, for wrapping your possessions around you like a security blanket against the cold, or for counting your collections to see what you can sell to pay the oil bill.

This January, in Washington, is especially a time to inventory, because many of Washington's favorite old names will be folding their tents and packing their caravans. When parties change in the White House and the congress, it's a good time to buy antiques and as they about Cadillacs, "previously owned goods."

Between now and Jan. 20, watch the want ads for antiques and merchandise. Look for signs on trees and apartment-house bulletin boards for moving sales. Go to the auctions. Check the Bombe Chest at 2629 Connecticut Ave., the Christ Child Opportunity Shop at 1427 Wisconsin Avenue, and the Salvation Army antique and book store at 512 First Street NW, not to mention all the choice small antique shops. It's an especially good time to find designer dresses and black-tie outfits as people leave the high life.

The Washington Antiques Show, Wednesday through Sunday at the Shoreham Hotel, is this area's biggest antique event of the year. It's a seminar as well as a sale and a major charity benefit. Some 44 exhibitors will bring their best furniture, jewelry, paintings, prints, porcelain and silver from the 18th and 19th centuries. Some voyeurs, who can't afford to buy, come just for the opportunity to see Clement Conger, curator of the White House, and collectors such as Chief Justice Warren Burger (honorary chairman), the William McCormick Blairs and the David Lloyd Kreegers spend their money. Mrs. Gene P. Bond and Mrs. James M. Johnson III are the co-chairmen of the 98 volunteers who put the show together.

The loan exhibition is of 19th-century folk art, an appropriate choice in this year, which has seen major sales of Americana, especially the blockbuster Garbisch Collection.

"Terms used to describe this art --" write Louise Burns, chairman of the loan exhibition, in the handsome and informative catalogue, "primitive, naive, provincial, innocent and non-academic -- rarely fit the style." She goes on to say they suggest "independence from cosmopolitan academic traditions, interest in design rather than optical realism, closely interwoven decorative and utilitarian function, and a simple rather than sophisticated approach. The style originated in rural areas and came from craft instead of fine arts traditions. For the fullest record of American life in the 18th and 20th centuries one can look more confidently to the Naive than to the professional artist.

"What draws us to it is its total lack of pretentiousness and self-consciousness. It was fashioned by artists who had no formal training but were inspired to extol the dignity of everyday life by making a purely utilitarian object a thing of beauty. Subject matter came straight out of the life around them. They had the craftsman's love for physical structure and substance of material together with an intuitive gift for simplification, eliminating unnecessary details and setting down only the essentials. They seldom bothered to sign their works, so most have remained anonymous."

Fourteen handsome folk-art objects will be on display.

The folk-art model of Independence Hall, probably made in Pennsylvania in the late 19th century, is 39 inches long and is owned by Mr. and Mrs. Richard Pugh Stifel.

Of the four patchwork quilts, three come from the Daughters of the American Revolution Museum on 17th Street NW, including the "odd fellow" patchwork pieced and stuffed quilt mady by An Lindsay of Pennsylvania in 1840. Mrs. Francis W. Murray Jr. lent the pieced, block crazy quilt top of silk, with almost an op-art effect, mady by Cynthia Bradley Baldwin about 1850, New Haven, Conn.

Two weathervanes, one a stag, the other a horse and rider, both 19th century, were lent by Mr. and Mrs. Charles Bartlett (who also lent a coverlet). Two more weathervanes, a cock and an eagle, in the show come from DAR and the Stifels. The Stifels also lent a 57-inch key trade sign. A cigar-store Indian, another trade sign, and a ship captain figurehead, were lent by Mr. and Mrs. John P. Wallach. The whirligig in the form of Uncle Sam with an American flag on one side and a Canadian on the other, was lent by the Leo Rabkins.

The excellent catalogue this year includes major articles on folk art, including "Folklore and Folk Art: The Origins of Two Movements," by Ralph Rinzler, director of the Smithsonian's Office of Folklife Programs. rOther articles cover the Barbisch Collection at the National Gallery, by Donna Mann, of the Gallery; the Smithsonian's Eleanor and Mable Van Alstyne Folk Art Collection, by Elaine Eff, Smithsonian folklorist; and "A Family Folk Art Portrait, Phebe Reich of Frederick, Md.," by Jean Taylor Federico, DAR curator. The catalogue is $5 at the door, $7 by mail from The Washington Antiques Show, 11940 Piney Meeting House Road, Potomac, Md. 20854.

Six events are scheduled.

Friday, 6 to 8 p.m.: Wendell D. Garrett, editor, the magazine Antiques, will moderate a panel of exhibitors on "Collecting Antiques, for Love or Money." The price of $12.50 includes wine, cheese and show admission.

Saturday: Verbal appraisals of antiques will be given for $5 for the first item, $3 for each additional, by Malcolm Stearns, silver; Edward Ellis, prints; John Hart, procelain; Robert D. Schwartz, Edith Weber, jewelry; John C. Newcomer, Americana.

Sunday brunch, at 11 a.m. will have a lecture "Furniture Fakes and Forgeries," by Benno Forman, Winterthur research fellow and teaching associate; brunch, catalog and admission are included in the $24 price.

Three events are sold out -- invitational preview dinner Tuesday night, and the lecture and luncheon by Beatrix T. Rumford, director of the Abby Aldrich Rockefeller Folk Art Center, Colonial Williamsburg, and the Young Collectors' Night.

Tours can be arranged, including foreigh-language guides, Wednesday through Friday. General admission is $4. Information is available by calling (301) 986-0698 or (301) 229-8262. The events benefits the Thrift Shop Charities: Child Health Center Board of Children's Hospital, Children's Hospital National Medical Center, Columbia Hospital for Women Clinics, The Hospital for Sick Children and St. John's Child Development Center, according to Dandridge Ince.