They may not be the prettiest of fish but they sure are cool. They leave the water at night to spawn during the spring and summer months, and while they love the L.A. Harbor, they can also be spotted on nearby Westside beaches. Peak grunion traffic normally occurs on the second and third nights of each four-day run, with the second hour typically better than the first. The upcoming schedule is below, based on predictions for Cabrillo Beach, and more info can be found for the remaining season at these sites:
https://www.californiabeaches.com/grunion-run-schedule/
https://www.wildlife.ca.gov/fishing/ocean/grunion
Daily Breeze and Cabrillo Marine Aquarium

May 18 Sa 9:35 p.m. – 11:35 p.m.
May 19 Su 10:10 p.m. – 12:10 a.m.
May 20 Mo 10:45 p.m. – 12:45 a.m.
May 21 Tu 11:20 p.m. – 1:20 a.m.

June 3 Mo 9:45 p.m. – 11:45 p.m.
June 4 Tu 10:20 p.m. – 12:20 a.m.
June 5 We 11:05 p.m. – 1:05 a.m.
June 6 Th 11:55 p.m. – 1:55 a.m.