When the sun comes out in Seattle, families head straight for the water. Understandable, as we only get so many months of this! Lakes and family favorite beaches across the region become hubs for swimming, splashing, and cooling off. But before you pack up for a day at the lake, it’s smart to check King County beach water quality.
King County makes that easy with an online resource that shows King County swimming beach water quality, temperature, and any beach closures. This free tool helps parents plan safer summer outings while avoiding unpleasant surprises.
Check Before You Go
King County’s Lake Swimming Beach webpage has an interactive map that displays water testing results for dozens of public swimming beaches across the region. Green circles on the map mean the water is considered safe. Red markers indicate beaches that are currently closed due to issues like high bacteria or toxic algae.
You can also click to view current water temperatures, which is especially useful since local lakes can remain chilly well into summer.
For extra convenience, sign up for email or text notifications to receive updates when a beach is closed or reopened, or to get a Friday summary of weekend conditions. Alerts are available in both English and Spanish.
All the green circles are beaches with healthy water (low bacteria) this week. Clicking “Water Temperature” lets you see how warm the water is. (Image courtesy King County)
What the County Tests For
Each week, King County samples the water at popular beaches and analyzes it for bacteria, specifically a type that signals the presence of fecal matter. This bacterium comes from people, pets, or wildlife and indicates that harmful germs could be in the water.
The county also tests for toxic algae at many beaches, especially if a visible bloom is present. The standard testing season for bacteria runs mid-May through mid-September, and algae testing continues into late October.
Swimming in contaminated water can lead to symptoms like diarrhea, nausea, stomachaches, rashes, or infections. Children, seniors, and those with weaker immune systems are especially vulnerable.
King County measures bacteria concentrations at the swimming beaches each week. (Image courtesy King County)
Why Beaches Close
Beach closures are most often the result of high bacteria levels or algae blooms. Contaminants can come from nearby wildlife, pet waste, or sewer issues. When results show a high risk of illness, Public Health – Seattle & King County recommends that beaches close temporarily.
The county investigates each closure to pinpoint the source of contamination. This might involve follow-up testing to determine if bacteria came from dogs, humans, or other animals. The health department also partners with parks staff and utility crews to reduce runoff, manage geese populations, or make infrastructure changes that improve water flow.
What About Dogs?
Dogs should not swim at public swimming beaches, especially when a closure is in effect. They’re more likely to drink lake water and get sick. Plus, dog poop contributes to the very water quality issues that cause closures.
In fact, dogs are prohibited at public beaches in Seattle and many nearby cities. Choose alternate areas for dog-friendly water play for your pup’s safety and the community’s health.
Seattle-area families love their lake days, but water safety is part of smart summer planning. The King County swimming beach water quality map gives you the latest updates so you can make informed choices before heading out.
