Iydlwood Beach Park

Managed by King County Department Natural Resources and Parks

Located on the shores of picturesque Lake Sammamish, Idylwood features a swimming beach, including a bathhouse and restrooms. Launch your car-top boat from the park’s small ramp. Spread out and play a game in the large open space or explore Idylwood’s playground area. Picnic shelters and picnic tables complete the picture for a perfect get-together. You will find plenty of parking here, as well.

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COVID-19

Keep your distance from other people.

Practicing social distancing is still essential. Only go to the beach if you are able to keep 6 feet or 2 meters away from others. Follow the instructions provided by your local health authorities. If your community has asked that you remain indoors and away from others, do so. Spending a day in any crowded place is the worst thing we can do for our most vulnerable right now and will counter our efforts to curb the virus’s spread.

Water Quality

Passed water quality tests at least 95% of the time
Historical Status
This status is based on the latest sample, taken on September 21st, 2021. King County Department Natural Resources and Parks updates the status of this beach as soon as test results become available. These results were posted to Swim Guide on September 23th, 2021 at 8:23 PM.

For water quality icon legend, click:

Current Weather

3°C

Clear

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Monitoring Frequency

Source Information

The King County Department of Natural Resources and Parks monitors water quality at designated swimming beaches in the county from May to September. Water quality data is collected weekly, usually on Tuesdays. Results are generally posted to the King County Lake Swimming Beach Bacteria Monitoring page by noon on Wednesday.

Local health officials use the following protocol to make closure determinations – A day’s average E. coli value is over 1000 CFU/100 mL – OR - The average of the E. coli values for the three most recent sampling days is over 200 CFU/100 mL. The three-day average is calculated using the geometric mean (geomean). The unit of measure is a CFU which stands for Colony Forming Units.

The King County Water and Land Resources Division (WLRD) collects and analyzes the samples. Public Health Seattle & King County is alerted when bacteria or state algal toxin thresholds are exceeded and determines the health and safety implications of the bacteria and algal toxin data collected, and they work with King County WLRD and the local park manager to post an advisory.

A beach is marked Green (open) when both of these protocols are met.
A beach is marked Red (closed) when these criteria are not met and the public health officials have closed the beach.

A beach may also be marked Red if there is a Harmful Algal Bloom (HAB) reported at the beach. A beach is marked Grey when current water quality data is not available.

For more information go to King County Swimming Beach Bacteria Monitoring website: kingcounty.gov/swimbeach.

Water Quality Graph