Six Flags Discovery Kingdom in Vallejo was forced to close all day Saturday after a power outage — traced by PG&E to "third-party damage" — knocked out electricity to the 135-acre park in the early hours of the morning.

The closure hit on a peak summer weekend, leaving ticketholders without recourse for the day. PG&E crews dispatched to the site found the damage was caused by a third party rather than the utility's own equipment — but the utility did not publicly identify what or who caused it. Restoration was not expected until as late as 8 p.m., well after a family day at the park could be salvaged.

Six Flags Discovery Kingdom in Vallejo shut its gates Saturday after a power outage darkened the Northern California theme park in the early morning hours, according to the park and PG&E.

The outage was reported at 2:17 a.m., according to the Vallejo Times-Herald. When PG&E crews arrived to inspect, they found what the utility described as "third-party damage" — meaning the failure wasn't caused by PG&E equipment or grid conditions, but by an outside party. PG&E did not identify the source of the damage.

Crews were still on site working to restore power as late as 11 a.m. The utility estimated power would return by 8 p.m. — too late for families who had planned a Saturday at the park.

Six Flags management posted on social media just before 8 a.m. to announce the closure, saying the outage was being resolved and the park would remain closed for the day. The announcement came as visitors were likely already on their way.

"We apologize for the inconvenience and thank you for your understanding," the park wrote, according to the Times-Herald.

Six Flags also posted a notice directly on its website — "Due to a loss of power Six Flags Discovery Kingdom will be closed Saturday, June 13th" — and said tickets dated June 13 would be honored on any future valid operating day during the 2026 season. The park said it would provide an update on whether it would reopen Sunday when more information was available.

Discovery Kingdom, which bills itself as "the only theme park in North America" combining thrill rides with marine and land animals, is one of the region's signature summer destinations. A summer Saturday closure represents a significant revenue and visitation hit during one of the park's busiest stretches of the year.

NBC Bay Area first reported the closure Saturday, citing park officials. The Times-Herald, citing PG&E data, added the "third-party damage" finding that distinguishes this outage from routine equipment failures.

The cause of the third-party damage and whether it was accidental or otherwise remains undisclosed. PG&E has not issued a public statement naming the source.