“It’s a New York thing — FOMO,” said Brianne Chai-Onn, 34, using the acronym for “fear of missing out.”

“A lot of people have this syndrome,” she said while waiting in line on Saturday. “That’s why we don’t sit in our apartments.”

The average wait on weekdays, according to MoMA, has been four to five hours for nonmembers and two to three hours for members, who use a fast-track line. Weekends are worse; a nonmember can expect to wait more than five hours. Some visitors last weekend reported waiting nine hours, longer than a standard work day.

On Sunday, the first people in line were admitted at precisely 9:30 a.m., when the museum opened. But the line had been declared full — and closed — a half-hour earlier.

The wait is partly a result of the artists’ decision to cap the exhibit’s capacity to 10 at a time — a mob would trigger the sensors into shutting off the rain entirely — and by the many visitors who ignore the museum’s polite request to limit visits to 10 minutes. So far, roughly 55,000 visitors have passed through “Rain Room,” according to the Modern.