Garrett is in a challenging position: She has been in the job only since August, part of a wave of new leaders of American regional theaters who are still getting to know their institutions and their audiences but are now facing an enormous, and unexpected, challenge. Garrett took the job imagining all kinds of ways she would make her mark on the venerable festival; now, she said, “I can’t even think about what course we were on before this thing happened, because it so swiftly shifted.”

Earlier this month, when the coronavirus outbreak prompted theaters around the country to shutter, some said they hoped to reopen after a few weeks. But more recently, many have canceled all spring productions, from Trinity Repertory Company in Providence, R.I., to the American Conservatory Theater in San Francisco. Two large New York nonprofits, Lincoln Center Theater and Roundabout Theater Company, have moved their spring and summer shows, including three slated for Broadway, to next season.

Now some summer favorites are reassessing their plans, saying an inability to rehearse, build sets and sell tickets is making shows untenable. On Friday, the California Shakespeare Theater, an outdoor festival in Orinda, Calif., announced that it would cancel its entire 2020 season.

Most summer festivals are still taking a wait-and-see attitude. In Scotland, the Edinburgh Festival Fringe said, simply, “We still don’t know what the future holds.” In Canada, the Stratford Festival “now finds itself in a holding pattern” and has suspended season preparations. In New York, the Public Theater says it is awaiting guidance from local officials before determining what impact the pandemic might have on its popular Shakespeare in the Park program, which is scheduled to begin May 19.

The Oregon Shakespeare Festival, founded in 1935, won the regional theater Tony Award in 1983 and presents contemporary work as well as classics; the festival has helped develop several shows that ultimately landed on Broadway, including the Pulitzer-winning “Sweat” and the Tony-winning “All the Way.”