Summer opera? You better believe it. But, believe it or not, Washington will have more opera productions between Memorial Day and Labor Day than it had in the fall and winter. The operatic lineup, beginning with the Metropolitan's "Lohengrin" tomorrow night, will include more than a dozen staged productions, ranging from grand opera to children's opera, as well as several concerts with strong operatic content.

This abundance is available despite the cutting back of the Met's Washington season from two weeks to one. Smaller companies are more than filling the vacuum, including the New York City Opera, the Wolf Trap Opera Company and the Summer Opera Theatre. The result is more variety of styles and quite a few operatic rarities, including at least one Washington premiere.

In the old days, opera seasons would grind to a halt in February, with the arrival of Ash Wednesday and the beginning of Lent. It was felt that such frivolities were unsuited to a season of penitence. For those (including potentates of church and state) who had to have their music fix even if they abstained from meat, the similar but holier art of oratorio was brought in (with considerable savings in the cost of scenery and costumes), and the band played on.

Lenten taboos have disappeared, at least in music, but the Washington Opera's season still stops short of Ash Wednesday -- for reasons economic, not religious. Opera seasons are equally brief in most American cities -- though not New York, where the Met runs nonstop well into the spring.

The Met's dominance of opera in New York triggered the most spectacular recent development on the summer opera scene. The New York City Opera, the Met's less affluent neighbor in Lincoln Center, has given up competing in the winter season and now runs its productions through the summer and into the early fall, overlapping with the Met for only a few weeks. Its week at Wolf Trap, beginning on June 11, will be its first visit to Washington since the Filene Center burned down in 1982.

In previous years, the annual Wolf Trap visit was a postseason event, like the Met's tour. This year, the company will be warming up here for its New York season. Its performances will amount to a mini-festival devoted to the Far East as seen through western eyes, with three operas that take tragic, comic and in-between views of China and Japan. The best-known of the three are the two that take the most extreme views: Puccini's tragic "Madama Butterfly" and Gilbert and Sullivan's comic "The Mikado."

Less often performed is Puccini's final, unfinished opera, "Turandot," which has not been seen in Washington for years. The infrequency of performance is not a reflection of its quality -- it contains what many consider Puccini's finest music -- but of the unusual demands it makes on the chorus, the prima donna's upper register and the budget for scenery and costumes. It is a love story in which love is a matter of life and death, and the happy ending comes only at the last minute. Comic relief is provided by three bureaucrats of the Chinese Empire named Ping, Pong and Pang, who might (with a few changes) have stepped out of "The Mikado."

The rest of the staged opera at Wolf Trap this summer will be the work of Wolf Trap's own company. At the Filene Center, on Aug. 8 and 10, it will perform Mozart's "The Magic Flute" in Andrew Porter's English translation, with scenery and costumes designed by Maurice Sendak. This production, originally commissioned by the Houston Grand Opera, was also used by the Washington Opera for its "Magic Flute" a few years ago.

The production will be familiar, as will the voice of Jerome Hines, a guest artist singing the role of Sarastro. Otherwise, the company will be made up of young singers recruited for the summer from all over the United States. Each year, Wolf Trap assembles one of the finest opera companies in the United States, features it in a few productions, disbands it at the end of the summer and begins planning for next year's company.

Most of the 1985 Wolf Trap opera season will be presented in the cozy environments of the Barns or the children's theater in the woods, and will focus on operatic rarities. On July 19, in the Barns, two one-act Italian comedies will be performed in English translation: Rossini's "Il Signor Bruschino" and Donizetti's "Le convenienze teatrali," subtitled "Viva la Mamma," a lampoon of backstage life in which a baritone portrays the scheming, ambitious mother of a rising young soprano.

Opening at the Barns on July 26 will be the Washington premiere of "Transformations" by Conrad Susa, based on poet Anne Sexton's book of the same name -- a retelling of some of Grimm's fairy tales for adults, sometimes for adults only. The music has been described as eclectic, including elements of jazz and pop as well as classical styles. The score specifies that one soprano role is to be sung "in the manner of Lena Horne." Elsewhere, three women are required to sing in the style of the Andrews Sisters, while a tenor imitates Bing Crosby. Both productions in the Barns are scheduled for four performances, divided between July and August.

Meanwhile, in the theater in the woods, two short operas of Offenbach, "Fleuret" and "The Isle of Tulipatran," will be performed for children -- adults tolerated if accompanied by a child. Operatic material, without scenery or costumes, will be featured in three concerts at the Filene Center. On July 19, Franz Allers will conduct the National Symphony in a Gershwin program, highlighted by scenes from "Porgy and Bess" featuring Donnie Ray Albert and a soprano to be announced. On Aug. 18, the Wolf Trap Opera Company will present its annual showcase, featuring its members in a variety of scenes and arias. And on Aug. 21, there will be a program of arias and duets featuring Shirley Verrett and Grace Bumbry.

The Summer Opera Theatre, performing in recent years at Catholic University's Hartke Theatre, has established high standards on a low budget. This year, while the Metropolitan and the Washington Opera are cutting back, it is cautiously expanding its season, offering two new productions rather than its customary one. The choice of repertoire is also daring, compared to the "Traviata," "Madama Butterfly," "Merry Widow" and "Tales of Hoffmann" that have been featured in earlier seasons. It will open on July 10 with "Ariadne auf Naxos," the intricate Richard Strauss work that contains not one but two operas within an opera -- a tragedy and comedy performed simultaneously.

"La Rondine," Puccini's closest approach to the elegant insouciance of Viennese operetta, will be the company's second production, opening July 31. This opera is produced even less often than "Turandot," and will offer the composer's fans an opportunity to see him in a new light.

Closing the Metropolitan Opera's week at the Kennedy Center will be Tchaikovsky's "Eugene Onegin," an opera not seen here for years (it will also be a highlight of the Washington Opera's fall season). Also relatively unfamiliar is Verdi's "Simon Boccanegra," one of the Met productions telecast on PBS this year, which will be presented here on Friday.

Otherwise, the Met's 1985 Washington repertoire consists of tried and true favorites: "Lohengrin" (Monday and Thursday), "Rigoletto" (Tuesday), "Cosi fan tutte" (Wednesday) and "La Bohe me" (Friday matinee). These productions should get the season off to a good start, but they will be only the beginning of a summer-long operatic extravaganza.