Coastal Upwelling Cycles: When San Diego Waters Get Cold

San Diego’s reputation for year-round sunshine masks a less obvious truth: our water temperature swings dramatically with seasonal upwelling cycles. Understanding when and why cold water arrives is essential for anyone serious about surfing, diving, or any water sport in the region. The difference between a 58°F paddle-out and a 66°F session isn’t just comfort—it’s about performance, safety, and knowing what to expect.

What Is Upwelling?

Coastal upwelling occurs when strong winds push surface water away from shore, allowing deeper, colder water to rise and replace it. San Diego sits in a prime upwelling zone. During spring and early summer, the North Pacific High-pressure system strengthens, driving persistent northwesterly winds. These winds push the warm surface layer offshore, and cold, nutrient-rich water from 300+ feet below wells up to replace it.

This process is predictable, seasonal, and transformative for water conditions.

San Diego’s Upwelling Timeline

Spring (April–May): Upwelling begins in earnest. Water temperatures at breaks like Sunset Cliffs, Blacks Beach, and Torrey Pines drop rapidly. By late April, expect 58–62°F water. This is when most San Diego surfers transition to 4/3 wetsuits or thicker.

Early Summer (June–July): Peak upwelling. This is the coldest period of the year in San Diego waters. The Scripps Pier thermometer regularly reads 56–60°F. Breaks from Windansea to Swami’s experience maximum cold. Offshore winds are consistent and strong. The upside: clean conditions, reduced kelp, and excellent visibility for divers.

Late Summer (August): Upwelling begins to weaken. Water temps start climbing back toward 62–65°F. The wind pattern destabilizes. Swells become less consistent, but conditions often turn more tropical and unpredictable.

Fall (September–October): Upwelling subsides almost entirely. Water warms to 66–70°F. This is the warmest period of the year. By October, many surfers ditch wetsuits entirely at spots like Pacific Beach and Mission Beach.

Winter (November–March): No upwelling. Warm tropical swells arrive from southern storms. Water temps drop gradually to 58–62°F by February due to seasonal cooling, not wind-driven upwelling. Conditions are warmer than spring/early summer, and wind patterns are erratic.

How Upwelling Affects Your Sport

Surfing: Cold water means wetsuits are non-negotiable April through June. The good news: upwelling-driven winds create clean, offshore conditions at breaks facing north and west. Blacks Beach, Sunset Cliffs, and Windansea are legendary during peak upwelling. The swell tends to be consistent and the lineup less crowded than summer months.

Diving and Snorkeling: Upwelling brings nutrient-rich water that fuels the food chain. Visibility at La Jolla Cove and Bird Rock peaks during June–July. Water is cold, but marine life is abundant. Kelp forests are healthier. Bring a proper wetsuit—60°F water will drain your core in under an hour without one.

Stand-Up Paddling: Cold water makes SUP more technical. The thermal stress is real on flat days when you’re paddling without activity to generate heat. Calmer upwelling season conditions (May–June) are ideal for distance paddling, but dress appropriately.

Swimming: Open water swims at Mission Bay and Pacific Beach are brutal during peak upwelling. Acclimation takes 5–10 minutes. Winter months (January–February) are paradoxically warmer for swimmers, despite being “winter.”

Predicting Upwelling Strength

Upwelling intensity varies year to year. Strong El Niño years suppress upwelling; La Niña years intensify it. Check wind patterns via Element’s forecasts—sustained northwesterly winds above 10 knots signal active upwelling. The Scripps Pier temperature buoy is your real-time reference. When it reads below 60°F from April to June, peak upwelling is happening.

Local surfers and divers also track upwelling indirectly: when visibility at La Jolla Cove drops to 30–40 feet and the water looks greenish, plankton blooms driven by nutrient upwelling are peaking. When water turns gin-clear, upwelling is weakening.

Practical Takeaways

• April–June: Expect 56–62°F water. 4/3 or 5/4 wetsuits are standard. Conditions are clean and offshore-driven.
• July–August: Water is coldest, then begins warming. Upwelling weakens mid-August.
• September–October: Warmest water of the year (66–70°F). Light wind days are common.
• November–March: No upwelling. Water temps vary by month, not wind cycle. Winter swells are larger but messier.

Plan your sessions around these cycles. Spring upwelling isn’t an obstacle—it’s the engine that drives some of San Diego’s best water sports conditions. Respect the cold, dress appropriately, and use Element to track wind and water temperature forecasts so you’re never caught unprepared.

Track upwelling patterns and water temperature in real time with Element. Download the app to stay ahead of San Diego’s seasonal shifts.