Lake Swimming Beach Bacteria and Temperature
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We test the water at more than two dozen popular lake swimming beaches during mid-May to mid-September. If water tests find high bacteria, this means there is poop in the water from people, pets, or wildlife. Poop can carry germs that can make people sick from swimming or playing in the water.
Bacteria testing at swimming beaches has ended for the season. Toxic-algae testing will continue at many beaches through October. For more information about toxic algae in lakes, visit the Northwest Toxic Algae website.
Swim safely during the rainy season! When it rains, poop (and germs) gets washed from land into the water. Swimmers, kayakers, and other winter beachgoers should use caution after heavy rainfall:
- Stay out of the water for at least 24 hours after heavy rainfall.
- Avoid areas where you see pipes or streams that drain directly to the beach.
- Check the Combined Sewer Overflow website, which shows places where the combined sewer has overflowed recently. Avoid swimming near an overflow for 48 hours.
Toxic algae in King County Lakes: Due to toxic algae blooms, Public Health - Seattle & King County recommends that you keep your pets away from the water in King County lakes were algae is visible. People should follow posted guidance at parks and beaches. Avoid going into the water at any lake where you can see algae, or where there is an advisory posted.