It’s already felt like summer this week, though it’s not official until the first open-air chord is strummed. We inched a little closer to amphitheater season this week with the Woodland Park Zoo unveiling the second phase of its popular ZooTunes summer concert series.

As of now, the Indigo Girls are set to kick off the picnic-blanketed series June 16. A few months removed from joining Brandi Carlile’s Girls Just Wanna Weekend festival in Mexico, the folk-rock staples return to the zoo for the second year in a row. Electrified string-band jammers Greensky Bluegrass arrive June 30, followed by country singer Cody Johnson on July 21.

August brings a trinity of solid double bills, led by folk-country great John Prine (Aug. 4), who earned three Grammy nominations on the strength of “The Tree of Forgiveness” album, replete with raspy porch-swing lines about smoking 9-mile cigarettes in heaven. Prine’s joined by a younger generation Americana star in Amanda Shires, who’s touring on an exceptional album of her own, “To the Sunset.” Earlier this year, Shires announced the formation of the Highwomen supergroup with Carlile. (Though Shires initially told a Louisville radio station Margo Price had joined the band, that claim was later refuted by Price’s camp and this month, Maren Morris’ involvement was revealed.)

Zoo-circuit fixture Taj Mahal and Marc Cohn perform Aug. 15 with not-to-miss special guests The Blind Boys of Alabama. Rootsy trio The Wood Brothers and rising country outlaw Colter Wall rock the lawn Aug. 25 ahead of the Lost ’80s Live nostalgia tour, featuring A Flock of Seagulls, Wang Chung and other one-hit wonders from the greatest hair generation.

Tickets for Taj Mahal, The Wood Brothers and Lost ’80s Live, which were announced this week, go on sale to the general public Friday, though a presale is already underway using the promo code “GIRAFFE.” Tickets for the previously announced shows are also on sale.