Pool closing · State guide

When to Close Your Pool in Washington

Last updated: July 15, 2026 · 21 cities covered

Closing deadlines across Washington stretch about 24 days: Bellingham needs the cover on first (September 17), Kennewick last (October 11), and the statewide median deadline is October 1.

Each deadline is the model's two-clock compromise — ten days after the water leaves the algae zone, capped a week before the local 50% first-freeze date. City pages carry the live widget that flags early-freeze years and the full winterizing sequence.

Dates are typical-year model outputs, not forecasts — each city guide carries the live widget that tracks the current year against them.

How to use these dates

Each "close by" deadline is the model's two-clock compromise for that city: ten days after its 7-day mean temperature falls back through 61°F (water goes algae-dormant soon after), but never later than a week before its 50% first-freeze date from the NOAA 1991–2020 normals. Closing inside the window seals cold, stable water under the cover; closing early seals a warm algae incubator instead.

Treat the dates as typical-year guidance, not forecasts. An early cold snap moves the real deadline — each city guide runs a live water-temperature widget that flags a 32°F night inside the 10-day forecast as urgent, and carries the full winterizing checklist in working order.