Shadow Cliffs Lake

Each dot is one sample taken by the monitoring agency. The dashed brick line marks the EPA single-sample limit.

Common questions.

Is Shadow Cliffs Lake safe to swim today?

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Shadow Cliffs Lake is currently not safe for swimming. One or more bacteria readings exceeded EPA thresholds in the most recent sample. See the readings below for which indicator and how far above the limit.

When was Shadow Cliffs Lake last tested?

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The most recent water-quality sample at Shadow Cliffs Lake was collected on May 28, 2026 (5 days ago). California monitoring agencies test Bay Area beaches weekly during swim season (roughly May through October).

What is the bacteria level at Shadow Cliffs Lake?

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The latest reading at Shadow Cliffs Lake shows E. coli at 2,200 MPN/100mL (EPA single-sample limit: 235).

Does rain affect water quality at Shadow Cliffs Lake?

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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 Shadow Cliffs Lake located?

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Shadow Cliffs Lake is located in the East Bay area of the San Francisco Bay region (coordinates: 37.6694°N, 121.8363°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 Shadow Cliffs Lake 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.