WITH extra time and relatives on your hands over the holidays, make a resolution to take in something new. The Phillips Collection, in keeping with what founder Duncan Phillips called "an air of comfort, ease and domesticity," has opened a cozy outpost of Suzanne's restaurant on the ground floor. First work up an appetite in front of Renoir's "Luncheon of the Boating Party." Or explore the Phillips' wood-paneled music room and double Victorian parlors, where one is encouraged to sit awhile, the better to absorb the artistry of Degas, Monet, Manet, Bonnard, Braque and Klee. After browsing, there will be plenty of time for grazing, on pastries and tea, or pasta salad. Cafe hours: Tuesday through Saturday, 10 to 4; Sunday, 2 to 4:30. (The Phillips Collection, at 1600-21st Street NW, will close at 1 on New Year's Eve and is closed New ear's Day and every Monday.

If the snow is blowing during the holidays, think Antarctica. With winds up to 200 miles an hour and temperatures 160 below, no wonder the wind-chill factor was invented on the icebox continent. On his second expedition to Antarctica, Rear Admiral R. E. Byrd spent the winter under the snow at the South Pole in a prefabricated wood-and-paper hut that's now on display at the Navy Memorial Museum in the new exhibit, "Polar Exploration."

Go because it's there.

The museum, located in the Washington Navy Yard, is open 9 to 4 weekdays and 10 to 5 weekends. Closed New Year's Day.

At the National Gallery, what's new is its $4 million acquisition, Rembrandt Peale's "Rubens Peale With a Geranium." It was purchased at Sotheby's this month, at a record auction price for an American painting. During the holidays, the masterpiece is hanging in Lobby D of the West Building. Enter from the Fourth Street plaza and walk up to the main floor, where the Peale brother waits at the top of the stairs.

In the late afternoon, crowds tend to scatter in favor of dinner, so you might try then to see "Treasure Houses of Britain." Extended hours continue for the exhibit, Monday through Saturday, 10 to 7, and Sunday, noon to 9. Closed New Year's Day.

If you're holding off on your visit, mail-order reservations for free tickets to "Treasure Houses" are available. Send your request at least two weeks in advance, stating the date, time and number of reservations, and an alternate date and time, along with a stamped, self- addressed envelope, to: THB Reservations, Education Department, National Gallery of Art, Washington 20565.

National Gallery events this weekend: In conjunction with "Treasure Houses," "Tom Jones" is playing Friday and Saturday at 2:30 and Sunday at 6, and a lecture on Hardwicke Hall will be presented Sunday at 4, these both in the East Building Auditorium. Also Sunday, at 7, the National Gallery Orchestra, Richard Bales conducting, will perform a program of the traditional music of Vienna, in the West Building's east garden court.

One of the newest museums in town, and one we'll bet the visiting aunts and uncles haven't seen yet, is the National Building Museum, in the Pension Building, on F Street NW between Fourth and Fifth. For the holidays, an evergreen garland that looks to be a mile long festoons the cavernous Great Hall. The exhibits go into all sorts of detail about constructing the Pension Building, designing federal buildings, ironworking, and building the Brooklyn Bridge. If you're tired of playing tourguide, museum docents will take over for you, Tuesdays at 11, Thursdays at 12:15 and Saturdays at 1. Hours: weekdays, 10 to 4 and weekends, noon to 4; closing at 1 on New Year's Eve and closed New Year's Day.