July is historically California's peak plankton bloom month. Warm surface water, abundant sunlight, and nutrient-rich upwelled water create optimal conditions for explosive algae growth. In most years, July's bloom is less severe than it appears because higher swell mixes the water column and breaks apart surface accumulations.

June 2026 will be remembered as the month the bloom came six weeks ahead of schedule. Across California's dive zones—from Monterey to San Diego—the combination of marine heatwave warmth at the surface and persistent cold-water upwelling at depth created a perfect storm for plankton productivity. The result: an early-June red tide event that hammered visibility from the Bay Area through Orange County, with only offshore pinnacles and depth-access sites offering reprieve.

Southern California's forecast for May 2026.