How Seasonal Upwelling Lowers San Diego Water Temps and Extends Wetsuit Season

San Diego’s water temperature swings are dramatic. In August, you might paddle out in boardshorts at Blacks Beach or La Jolla Shores. By October, that same lineup demands a 4/3 wetsuit—sometimes a 5/4 by November. The culprit isn’t autumn arriving late; it’s seasonal upwelling, a predictable oceanographic pattern that defines San Diego’s fall and winter conditions.

What Is Upwelling and Why It Happens Here

Upwelling occurs when wind and currents push warm surface water offshore, allowing cold, nutrient-rich water from the deep ocean to rise and replace it. San Diego sits in a geographic sweet spot where this happens reliably from spring through fall, peaking in summer and early fall.

The California Current flows south along the coast year-round, but the trade winds—particularly the strong north and northwest winds of late spring through early fall—drive the upwelling mechanism. When wind pushes surface water away from shore, the pressure drop forces deeper water upward. This water, often 500–1,000 feet down, is cold: typically in the low 50s Fahrenheit.

The result is a coastal temperature gradient that often shocks newcomers. Offshore spots like Trestles or Oceanside can be 5–8 degrees warmer than the exposed reefs of La Jolla or the San Diego coast proper. That difference determines whether you’re comfortable in a spring suit or shivering through a dawn patrol session.

The San Diego Seasonal Pattern

June–August: Upwelling intensifies. Water temps drop from the mid-60s in May to the upper 50s by late July. Blacks Beach, which faces the deep submarine canyon, often dips to 55°F. Offshore breaks like Sunset Cliffs and Windansea see slightly warmer water but still cold enough for a 3/2 or 4/3 depending on your tolerance.

September–October: Peak upwelling. This is when many San Diego surfers transition to their winter quiver. Water temps bottom out in the low 50s across the county. The wind is still strong, keeping that deep cold water flowing in. Don’t be fooled by September’s warm air—the ocean is at its coldest of the year.

November–February: Upwelling weakens but persists. Temps stabilize in the mid-50s. Winter swells arrive, and consistent offshore winds keep conditions clean and cold. This is the real wetsuit season for San Diego—not because of rain or air temp, but because the ocean refuses to warm.

March–May: Transition. Upwelling winds ease, and water temps begin climbing. By late May, you’ll see mid-60s again. Some surfers can drop to a 3/2 or even spring suit by May, though early mornings still demand more coverage.

Why This Matters for Your Lineup

Upwelling doesn’t just drop the thermometer—it shapes which breaks are rideable and when. Spots exposed to the open ocean, like Sunset Cliffs or Windansea, feel the full force of upwelling and stay coldest. Protected bays warm faster and stay warmer longer.

Crystal Pier in Pacific Beach is typically 2–3 degrees warmer than nearby Tourmaline Surf Park, despite being just south. Spots inside Mission Bay stay warmer still. If you’re sensitive to cold, a session at Pacific Beach in October might be comfortable in a 4/3, but Blacks Beach demands a 5/4 or even a hooded vest.

Offshore breaks like Trestles (in the Trestles area south of Oceanside) and Tamarack Avenue benefit from warmer water pushed down from Orange County, staying 3–5 degrees warmer than exposed San Diego County reefs. If the water feels unbearably cold in early fall, a 45-minute drive south can mean the difference between a 4/3 and a 3/2.

Practical Implications for Your Wetsuit Rotation

Most San Diego surfers maintain a year-round 4/3 or 5/4 from September through April. A 3/2 works for May and early June if you don’t mind cold mornings. July and August allow spring suits or boardshorts for daytime sessions, though dawn patrol still demands a 3/2.

The upwelling is predictable enough that you can plan your quiver around it. Buy your winter suit in August, not October—inventory runs low once water temps drop. Keep your spring suit accessible through May; the transition is real, and early mornings are cold.

The Upside

Cold water brings nutrients, which fuel the food chain. Upwelling brings baitfish, which brings bigger swells (through improved pressure gradients) and better conditions overall. That 55-degree water at Blacks Beach isn’t punishment—it’s the signature of a healthy, productive ocean that makes San Diego’s fall and winter some of the best on the West Coast.

Track water temps daily with the Element app to dial in your wetsuit choice and stay comfortable in the lineup all season long.