Warm Water Upwelling: When San Diego Ditches the Wetsuit in September
September is the month San Diego surfers live for. Not for the swell—though that’s coming—but for water temps that finally, finally let you peel off the rubber and feel the ocean on your skin.
This phenomenon is called warm water upwelling, and it’s the reason your local breaks transform into bathwater conditions right when most of the country is still dealing with summer crowds and inconsistent swells. Understanding when and where it happens can make September your most comfortable and productive month in the water.
What Drives Upwelling in San Diego?
Upwelling occurs when southwesterly winds push warm surface water offshore, forcing deeper, cooler water up from below. But here’s the San Diego-specific part: the California Current dominates our coast year-round, keeping water temps suppressed through spring and early summer. By late August and September, a combination of weakening coastal winds and the seasonal shift toward autumn swells creates the perfect conditions for warmer water from the south—the Baja Current—to push northward.
The result? Water temperatures spike from the low 60s (July) to the mid-70s and sometimes even low 80s by mid-September. At Blacks Beach, you might see 78°F. At Windansea, the reef’s orientation and depth can push it even warmer.
When to Expect Peak Warmth
The sweet spot runs from early September through late September, with peak temperatures typically hitting around September 10–20. Early September can still be iffy—you might see 70–72°F and need a light spring suit. But by mid-month, boardshorts-only conditions are the norm at most breaks.
The warmth doesn’t last forever. By early October, the pattern breaks. Stronger fall swells arrive, northwesterly winds reassert control, and cooler water returns. You’ll be back in a 3/2 by mid-October.
Where to Find the Warmest Water
Not all San Diego breaks warm equally. South-facing and reef-protected spots tend to hold warmth better:
Blacks Beach offers some of the most consistent warmth thanks to its depth and south-facing exposure. The shorebreak stays balmy, and the reef zone benefits from thermal retention. September here is genuinely tropical.
Windansea is another champion. The reef’s configuration and the surrounding kelp beds create a microclimate that holds warmth longer than adjacent breaks. Plus, the consistent swell and protected shoulder make it a no-brainer in September.
Ocean Beach Pier and the surrounding jetty area warm quickly due to shallow, sandy conditions and good exposure to warm swells from the south. Expect 75–78°F here.
Mission Beach and the surrounding beach breaks respond rapidly to warm water influxes. These sandy zones heat up fast and are often 2–3 degrees warmer than reef breaks in the same period.
Pacific Beach is similar to Mission Beach—warmer than you’d expect, especially along the north side near the Crystal Pier.
The coldest pockets in September? North County—Torrey Pines, Swami’s, and Cardiff—tend to lag by 3–5 degrees due to greater exposure to cooler California Current influence. Still swimmable, but you might want a rashguard or thin spring suit.
What Upwelling Means for Your Session
Beyond comfort, warm water upwelling changes how you surf. You stay in longer without fatigue from cold stress. Your joints move better. Recovery is faster. Paddling out at 6 a.m. doesn’t feel like a shock to the system.
The trade-off? Upwelling also correlates with the arrival of autumn swells. September can get chunky quickly. The same conditions that bring warm water often bring larger, more powerful waves. Blacks Beach and Windansea get heavy. Ocean Beach and Mission Beach become fast and powerful. If you’re used to summer mushiness, September’s swell can humble you fast.
Plan Around the Seasonal Window
This is a finite window. If you’ve been putting off that early-morning session or longer paddle because the water was too cold, September is your month. Check the Element app daily—water temperature data shifts quickly once the pattern breaks in late September or early October.
If you’re new to San Diego surfing or just looking to maximize comfort, prioritize Blacks Beach and Windansea in the second and third weeks of September. These breaks offer the warmest, most consistent conditions and handle the bigger autumn swells with grace.
Don’t wait for October. The window closes fast, and you’ll be back in a suit before you know it.
Track water temps daily with the Element app and never miss peak upwelling conditions at your favorite San Diego breaks.