Discover San Francisco Bay water temperatures for swimming near Alcatraz or elsewhere in SF Bay.
See averages, charts, and tips for open water swims year-round.
From 2010 to 2024, San Francisco Bay water temperatures stayed in the 50s°F, with occasional peaks into the low 60s°F during late summer and fall. We assembled 14 years of NOAA data collected near the Golden Gate Bridge, which we’ve learned to trust and confirm on our daily swims. Although the NOAA sensor stopped operating in 2024, the historical averages below remain reliable for planning open water swims in San Francisco and Alcatraz.
Average Water Temperatures in San Francisco Bay
Water temperature in the Bay shifts daily with the tides, weather, and wind. In winter, swimmers often see 1–2°F changes over a few hours as the tides change. From summer through fall, shifts of 4°F or more are common. These patterns are typical in the central Bay—between the Golden Gate Bridge and Alcatraz—where currents and wind drive constant variation.
Swimming Near Alcatraz: Temperature Guide
Detailed Temperature Breakdown
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Temp (°F) | 52.2 | 50.4 | 50.2 | 52.6 | 54.6 | 56.8 | 58.7 | 60.4 | 60.9 | 58.5 | 55.1 | 52.6 |
| Avg Temp (°C) | 11.2 | 10.2 | 10.1 | 11.4 | 12.6 | 13.8 | 14.8 | 15.8 | 16.1 | 14.7 | 12.8 | 11.4 |
Planning for Open Water Swimming in San Francisco
Swimmers preparing for an Alcatraz swim or other San Francisco open water events can expect chilly Bay waters, averaging in the mid-50s°F most of the year. In central San Francisco Bay, water temperatures rarely rise above 62°F, so preparation is essential for any open water adventure.
At Pacific Open Water Swim Co., we swim year-round—24/7/365—staying acclimated and swimming skin (no wetsuits). Winter lows near 49-50°F can feel brutal, but the cold passes quickly, and a few degrees above the minimums make it manageable. Late summer and fall bring balmy 60-62°F waters for us regulars. New to San Francisco Bay’s water temperatures? Target fall through mid-November for the mildest conditions—ideal for an Alcatraz swim or open water challenge.
Triathlon Wetsuits for San Francisco Bay and Alcatraz Swims
San Francisco Bay’s water temperatures (50-62°F) call for a triathlon wetsuit for most swimmers hitting Alcatraz or open water events. Unlike restrictive surfing or diving suits, triathlon wetsuits offer flexibility and speed for efficient strokes in cold water. For winter swims (50-55°F), a full-sleeve 5/3mm wetsuit (max 5mm per triathlon rules) keeps you warm without limiting arm movement. In fall (58-62°F), a 3/2mm suit (or sleeveless) blends comfort and agility.
Recommended Triathlon Wetsuits:
- Zone3 Advance: Around $250, with 5mm neoprene legs for buoyancy and 2mm shoulders for flexibility—perfect for beginners.
- Orca Openwater Core: $200-$300, with 3-4mm Yamamoto neoprene for warmth and a snug fit in SF Bay’s chill.
- Roka Maverick Comp II: $400+, with 1.5-5mm neoprene and top-tier shoulder mobility—great for seasoned Alcatraz swimmers.
- Sports Basement Presidio Blueseventy Rentals (as of March, 2025, $30-$55/day):
- Blueseventy Fusion (Full-Sleeve): Entry-level with 5mm legs, 3mm chest/back, 1.5-2mm arms.
- Blueseventy Reaction (Full-Sleeve): Performance-focused with 4mm chest, 5mm core/legs, 2mm arms.
- Blueseventy Reaction (Sleeveless): Sleeveless with 4-5mm core/legs.
If you’re new to wetsuit swimming, you should test their wetsuit fit with a short swim—rentals are a great start. Wetsuit makes your first Alcatraz swim manageable, especially if you’re from warmer climates. Again, check out Sports Basement Presidio for rentals or visit their site if you’re flying in to swim.