Lake Anza

Common questions.

Is Lake Anza safe to swim today?

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Lake Anza is currently safe for swimming. Recent samples within safe ranges.

Does rain affect water quality at Lake Anza?

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Yes. Heavy rainfall washes bacteria and pollutants from land into the water, raising contamination risk for 24–72 hours. The past 48 hours recorded 0.00 in of rain; the past 72 hours recorded 0.00 in. Our advisory threshold is ≥1.00 in over 48h (or ≥0.50 in over 72h) for enclosed or storm-drain beaches.

Where is Lake Anza located?

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Lake Anza is located in the East Bay area of the San Francisco Bay region (coordinates: 37.8962°N, 122.2500°W). You can get turn-by-turn directions via Google Maps or Apple Maps directly from this page.

How is the water quality data for Lake Anza collected?

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Bacteria samples are collected by California state and county health agencies under the AB 411 Safe-to-Swim program and reported to the state's Safe-to-Swim database (data.ca.gov). Rainfall figures come from Open-Meteo forecast and archive data. Bay Area Swim aggregates both sources and updates every morning.