There is no sleepy summer, only a barely perceptible slackening in the pace of exhibition and gallery openings. Don’t expect blockbusters, but don’t settle in for a season of sweet intellectual lassitude, either.

June is the richest month, with three major shows focused on three very different American artists. The Corcoran brings an exhibition devoted to Richard Diebenkorn (June 30-Sept. 23), the West Coast painter who dipped in and out of abstraction before producing his monumental opus, the Ocean Park Series. First seen at the Orange County Museum of Art, the Ocean Park exhibition features nearly 80 of the more than 140 paintings made by the artist between 1967 and 1988, while a resident in a seaside neighborhood in Santa Monica, Calif. They are magnificent studies in light, color and geometry.

The Phillips Collection devotes at least as much love to Jasper Johns in an exhibition called “Jasper Johns: Variations on a Theme” (June 2-Sept. 9). The show focuses on Johns’s devotion to printmaking, lithographs and intaglio. The iterative process of printmaking allows for subtle variation, as well as meta-commentary on ideas of originality, authenticity and the role of the artist in manipulating his material. “Variations on a Theme” includes work from the 1960s to the present, with some of Johns’s classic imagery (flags, numbers and targets) alongside newer and less well-known work. There are almost 100 works in the exhibition.

And the National Gallery of Art looks back to George Bellows, the American realist painter whose career spanned not only the turn of the 20th century, but the evolution of American art from Victorian to modern inclinations (June 10-Oct. 8). Perhaps most famous for his boxing and sporting scenes, Bellows was also passionately committed to social and political themes. The exhibition, which includes about 150 works, is billed as the first major retrospective devoted to the artist in three decades — a period in which scholarly and curatorial appreciation for the realist painters of the last century has grown immensely.

July is quieter, and August rather moribund. But the Sackler Gallery’s 25th anniversary season continues with a show devoted to the lustrous and finely detailed painting of the Mughal empire (July 28-Sept. 17). “Worlds Within Worlds: Imperial Paintings From India and Iran” features about 50 works from the literate, sophisticated and cosmopolitan empire that once stretched across what is now India, Pakistan and eastern Iran.

Another Sackler exhibition, “Nomads and Networks: The Ancient Art and Culture of Kazakhstan,” is promising because it draws on the holdings of major museums in Kazakhstan, ensuring that much of what is offered will be new to the vast majority of visitors (Aug. 11-Nov. 12).

Out of town, the Walters in Baltimore undertakes an experiment in curating: “Public Property” is the museum’s effort to involve the public in the complexities of putting together an exhibition (June 17-Aug. 19). The museum will allow the public to choose the title, the focus (it’s already decided on “creatures”) and the works on display. Public input will continue through the two-month show, which will evolve based on feedback. If you think this is a good idea, then proceed with skepticism; if it strikes you as dubious, then keep an open mind. Art museums are desperate to engage audiences beyond ticket sales and gift shop visitation, and summer is a good time to take chances.