How Upwelling Events Affect Water Temperature and Clarity in San Diego

Upwelling is the most powerful force shaping San Diego’s water conditions—and if you freedive here, understanding it will transform your planning and safety.

Upwelling occurs when strong winds push surface water away from shore, creating a vacuum that pulls nutrient-rich, cold water up from the depths. In San Diego, this happens predictably, primarily between March and September, with peak intensity typically in May through July. The California Current already delivers cold water year-round, but upwelling events supercharge this effect.

How Upwelling Cools San Diego’s Waters

During peak upwelling season, water temperatures along our coast can drop 10–15°F in a matter of days. Summer surface temperatures that might reach 70°F in a calm period can plummet to 55–60°F once upwelling kicks in. This isn’t gradual—it’s dramatic and noticeable.

The coldest upwelling typically centers on our exposed western reefs: Sunset Cliffs, the Coronado Islands, and Point Loma. These headlands and offshore features funnel wind and create ideal conditions for water to well up. Protected bays like Mission Bay and San Diego Bay warm faster and upwell less aggressively, making them warmer refuges when the open coast turns frigid.

If you’re freediving La Jolla Cove or Torrey Pines, expect cooler water than downtown beaches. The same upwelling that chills Point Loma affects our best kelp forest and reef sites.

Visibility: The Double-Edged Sword

Here’s where upwelling gets interesting for freediving. The cold, nutrient-rich water that rises triggers explosive phytoplankton blooms. More nutrients = more plankton = reduced visibility. During strong upwelling events, visibility at popular sites like La Jolla Cove can drop from 40+ feet to 15–20 feet in a week.

However, upwelling also delivers oxygen and food to the water column. Fish, kelp, and marine life thrive during and after upwelling events. So while you might have less visibility, you’ll often see more life.

The visibility pattern isn’t random. Upwelling-driven plankton blooms typically peak 1–2 weeks after the wind event begins. If you check Element’s wind and water clarity forecasts and see strong northwesterly or northerly winds ramping up, plan your dives accordingly. Scout conditions a few days later when the bloom is established, or wait 10–14 days for the plankton to settle or be flushed away.

Seasonal Timing for San Diego Freedivers

Spring (March–April): Early upwelling season. Water temps drop from the mild 60s to the 50s. Visibility is variable—still decent some weeks, murky others. Good time to dial in your 5mm or 7mm wetsuit.

Early Summer (May–June): Peak upwelling. Expect 55–62°F water and frequent visibility swings. The trade-off: kelp forests are lush, fish are abundant, and conditions reward patience. This is when serious freedivers in San Diego commit to thicker wetsuits and plan dives around forecast windows.

Mid-Summer (July–August): Upwelling persists but often becomes less intense as the month progresses. Some years see brief warm-water “breaks” where upwelling relaxes. Water temps might briefly climb to 65–68°F before dropping again. Check Element daily during this period—conditions shift fast.

Fall (September): Upwelling winds ease. Water temperatures gradually climb back toward 65–70°F. Visibility often improves as plankton blooms settle. September is often the sweet spot for San Diego freediving: warmer water, clearer visibility, and fewer crowds.

Practical Planning for Upwelling Season

Don’t fight upwelling—work with it. Use Element’s detailed forecasts to spot 3–5 day windows when winds ease and visibility is expected to improve. These breaks happen regularly throughout the season.

Know your local sites. Kelp forests at Torrey Pines and La Jolla Cove are more sheltered than exposed reefs like the Coronado Islands. Plan deeper, longer dives when upwelling is active; use calmer periods for shallower exploration or skill work.

Invest in the right gear. A 5mm or 7mm wetsuit isn’t optional from May through August in San Diego. Gloves and a hood make a difference. Cold water demands respect—hypothermia risk is real, even in summer.

Track the broader pattern. Upwelling isn’t random. Strong northwesterly wind patterns in late April almost always trigger intense upwelling by mid-May. Watch the extended forecast and plan accordingly.

The Bottom Line

Upwelling is why San Diego’s ocean is alive, productive, and challenging. It’s also why our water conditions change so dramatically week to week. Use Element’s real-time wind, temperature, and clarity forecasts to stay ahead of these shifts—and you’ll find better conditions, safer dives, and more consistent access to the vibrant marine life that makes freediving here unforgettable.

Check Element’s current conditions and forecasts before every dive to stay informed about upwelling patterns and water clarity in your area.