Guests will still need reservations to gain entry into SeaWorld's parks.
Theme parks can't fully reopen in California, but they're finding ways to welcome back guests without rides or attractions.
The event will feature only open-air scare zones and the "Fiends" stage show.
Also delayed will be Emperor, Pantheon and Ice Breaker.
SeaWorld will now be open Thursdays through Sept. 6.
The hard-ticket event will open only part of the park and six rides, including three coasters.
Busch Gardens Williamsburg is one of three SeaWorld-owned parks that remain closed.
Two Epcot area resorts are now set to remain closed until further notice.
Disneyland's theme parks have been closed since mid-March with no reopening in sight.