Critics are over the rainbow for Renée Zellweger again.

She’s wowing film festival audiences with her portrayal of the late Judy Garland, a bravura performance insiders predict will bring her a second Oscar nomination for Best Actress.

The 2004 Best Supporting Actress winner for “Cold Mountain” told The Post how she prepared for the Garland biopic, which was directed by Rupert Goold and based on Peter Quilter’s play “End of the Rainbow.”

The film covers the legendary singer’s final years, when a cash-strapped Garland performed in London in 1968. She died a year later, at age 47.

Going beyond spot-on recreations of the Hollywood icon’s signature looks, Zellweger does her own singing in the movie.

She told The Post she immersed herself in Garland’s discography as she drove to visit her dogs in a rehab clinic.

“I would spend hours on the 405 and 101 [freeways] listening to her. I did this every day in the car,” the native Texan and former cheerleader said.

These hours were crucial to Zellweger’s process of channeling the “A Star is Born” and “Wizard of Oz” star onscreen.

“Because I wanted to understand the evolution and I wanted to understand how it started, where it went and what that looked like,” she said. “For Judy, it was always about being able to connect with the songs and the feeling.”

“Judy” is set to hit theaters Sept. 27.

No word yet on whether Zellweger’s Netflix series, the critically drubbed “What/If,” will be renewed for a second season. But after several years as a tabloid punching bag, surely this renewed brush with big screen critical acclaim will ease the blow if the streaming giant doesn’t pick her show up.