San Onofre State Beach • Statistics for May

May: Swell is There, Wind is Not

May is the start of Southern California's classic bumpy-surface season, though the ocean underneath still has real juice. The average swell height is 3.6ft (1.1m), and the period stretches to 13.5s - a powerful, long-period groundswell. The swell direction is ideal: WSW 40%, SW 30%, SSW 8%, and only 22% from the straight W. That means San Onofre is seeing a higher percentage of direct southern-hemisphere and tropical-influenced southwest swell than at any point in the fall and winter.

However, wind quality collapses to just 8% ideal. The offshore quadrants are essentially absent, while onshore S, SSW, SW and WSW winds combine for over 55% of all observations. Add in nearly 20% westerly wind and you get a persistent onshore/cross-shore texture that keeps the surface lumpy for much of the day. Water temperature warms to 14.8°C, air temperatures average 17.1°C, and rainfall is low at 0.27 mm/day. The wave heights may read as fun, but the wind must be respected - dawn glass is the only reliable way to surf May at San Onofre.