The good news: Libations is hot.

The bad news: Libations is also humid. If you're the type of free spirit who only likes to sweat after you start dancing, stop here and proceed directly to October. The party at Libations goes on outdoors.

Actually, humidity is a small price to pay for the nightly live music -- usually rock or "light rock" -- in Libations' courtyard, which it shares with a Chinese restaurant and about a dozen 30-foot trees in the center of the Lafayette Centre office-commercial complex on 20th Street, between L and M. There are about 150 seats on two levels in the courtyard, which is the newest, and among the nicest, in the city.

If you absolutely must have air conditioning -- or if you want to discuss Faust with your date, or avoid the occasional $3 cover after showtime -- there are also about a hundred seats inside, plus a 24-foot bar just like the one outside.

Libations, formerly Artie's After Dark, relies on a knot of regular bands -- the likes of Harry Traynham and Pylot, Downtown, Jr. Cline and the Recliners, the Jack Bond Group, Tom Principato -- to attract a largely 25- to 40-year-old mix of couples and singles who share a fondness for dancing and/or drinking any of Libations' 12 brands of draft beer ($1.70 domestic, $2.25 imported) from plastic cups -- glass breaks easily on brick. The mix gets younger and singler on Saturday nights.

"A young, professional crowd, mostly," says manager Alan Korobkin, 34, who with co-owner Harvey Borkin decided this spring to upgrade the evening menu to attract diners as well as dancers. (Entr,ees start at $8.25, for linguine with clam sauce, and peak at $11.95 for New York strip.)

Korobkin also knows the value of a pleasant courtyard, especially one he owns. "There was one nice day this past March, just one 80-degree day, and we opened up the courtyard," he says. "There wasn't an open seat from 4 that afternoon till 3 a.m."

If there was one, there's a good chance it was occupied, temporarily, by one of Libations' generally cheerful, capable and exhausted waitresses, probably busy adding up an incredible column of pi?na coladas.

The pi?na coladas are $3.95 apiece. There is a word for a frozen drink at this price, when served outdoors in a climate such as Washington's during a month such as August. The word is "cheap." LIBATIONS -- Lafayette Centre courtyard, 1120 20th Street NW, open 11 to 2 Monday-Thursday, 11 to 3 Friday, 8 p.m. to 3 Saturday, 8 p.m. to 2 Sunday. 296-7666.