Thermal Upwelling in La Jolla Cove: Why August Water Temps Drop

If you’ve been in the water at La Jolla Cove in August, you’ve felt it: that sudden shock of cold water that catches you off guard, even though it’s peak summer. While air temperatures soar into the 80s, the ocean surface can drop 8–10°F in just a few weeks. This isn’t random. It’s thermal upwelling, and it’s one of San Diego’s most predictable—and most underestimated—oceanographic events.

What Is Thermal Upwelling?

Thermal upwelling occurs when deep, cold water from the ocean floor rises to the surface. In San Diego, this happens primarily along the coast between May and September, with the most intense cooling happening in July and August. The mechanism is straightforward: sustained northwesterly winds push warm surface water away from the coast. As surface water moves seaward, it creates a void that cold, nutrient-rich water from 200–300 feet below rushes in to fill.

This isn’t a local phenomenon unique to La Jolla. Upwelling happens along the entire California coast, driven by the same wind patterns. But La Jolla Cove, with its exposed headland and shallow embayment, experiences it acutely. The cove’s geography actually amplifies the effect, making it one of the coldest spots on San Diego’s coast during peak upwelling season.

The August Temperature Cliff

Here’s what you’ll actually experience: July water temperatures in La Jolla hover around 68–70°F. By mid-August, that drops to 58–62°F. That’s not a gradual decline—it’s a shock. Swimmers, surfers, and snorkelers who showed up in July without a wetsuit will be reaching for a 4/3mm by August.

The cold water isn’t a fluke; it’s predictable. Check the Element app during August, and you’ll see water temps at La Jolla consistently lower than spots just a few miles north at Windansea or south at Tourmaline Inlet. This happens because upwelling intensity varies by location and local bathymetry. La Jolla’s shallow, rocky bottom and the shape of its cove make it a cold-water trap.

Why This Matters for Your Water Sports

For swimmers and beach-goers, this means planning accordingly. A 60°F ocean requires neoprene—no question. Hypothermia isn’t theoretical at these temperatures; extended exposure without protection is genuinely risky. If you’re doing distance swimming or long training sessions at La Jolla Cove in August, a 3/2mm or 4/3mm wetsuit isn’t optional.

For surfers, the upwelling is mixed news. Yes, the water is colder. But upwelling brings nutrient-rich water to the surface, which fuels plankton blooms that attract baitfish, which attract bigger fish. La Jolla’s kelp forests thrive on this influx of nutrients. The ecosystem becomes more active and productive. You’re also more likely to see marine life—sea lions, harbor seals, even the occasional leopard shark—during upwelling season.

For snorkelers and divers, the cold water brings better visibility. Upwelled water is typically clearer than warm, stratified summer water. Kelp beds at La Jolla in August offer some of the best underwater visibility of the year.

When Does It End?

Upwelling weakens in September as the northwesterly wind pattern relaxes. By October, water temperatures begin recovering. By November, La Jolla’s water typically reaches 64–66°F and stabilizes through winter. The cold snap is intense but temporary—roughly 8–10 weeks of peak intensity from late July through early September.

If you’re planning a La Jolla Cove trip in August and want warmer water, you have options. Mission Beach and Pacific Beach stay slightly warmer because they’re more exposed to the open ocean’s surface layer. Torrey Pines State Natural Reserve’s beach is similarly warmer. But if you’re committed to La Jolla, embrace the cold and gear accordingly.

Preparation Tips

• Check the Element app before you go. Real-time water temperature data lets you decide on wetsuit thickness before you leave home.
• Plan for a 4/3mm or thicker wetsuit if you’re spending more than 30 minutes in the water at La Jolla in August.
• Bring a rash guard or thermal base layer even under your wetsuit. Layering extends comfort and safety.
• Consider timing your visit to early July or late September if you want warmer water at La Jolla Cove.

Thermal upwelling is a reminder that San Diego’s ocean isn’t uniformly warm, even in summer. It’s a dynamic system shaped by wind, bathymetry, and seasonal patterns. Understanding these patterns doesn’t just make you a smarter athlete—it keeps you safer and helps you plan better sessions.

Track real-time water temperatures and upwelling forecasts in the Element app to stay ahead of the cold and maximize your time in the water.