Lake Temescal

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

Common questions.

Is Lake Temescal safe to swim today?

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

When was Lake Temescal last tested?

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The most recent water-quality sample at Lake Temescal was collected on May 26, 2026 (7 days ago). California monitoring agencies test Bay Area beaches weekly during swim season (roughly May through October).

What is the bacteria level at Lake Temescal?

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The latest reading at Lake Temescal shows E. coli at 170 MPN/100mL (EPA single-sample limit: 235).

Does rain affect water quality at Lake Temescal?

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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 Temescal located?

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Lake Temescal is located in the East Bay area of the San Francisco Bay region (coordinates: 37.8465°N, 122.2304°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 Temescal 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.