Washington Pool Season: Opening & Closing Dates by City

Local dates for every featured Washington city — when the water warms up, when it cools off, and how long the season actually lasts.

City Opening window Closing window Season
Seattle Jun 11 – Jun 30 Sep 2 – Sep 18 ≈ 63 days
Spokane Jun 14 – Jul 5 Aug 23 – Sep 12 ≈ 70 days
Yakima May 31 – Jun 27 Aug 26 – Sep 15 ≈ 83 days

Windows show the stretch when each city's daily average passes through the low-to-mid 60s°F (1991–2020 NOAA records, nearest station to each city). Click a city for its month-by-month table and full season notes.

Season geography

Across Washington's featured cities, typical openings spread from Jun 15 to Jun 30, closings from Sep 2 to Sep 5, and the unheated season runs 63–83 days depending on where you are. Elevation, coastal water, and urban heat all pull real dates around, which is exactly why a state-level answer isn't enough.

For your exact town, the pool season lookup takes a ZIP code. Opening day itself is a chemistry job — the dosing calculator turns your first test reading of the year into exact amounts.

Washington planning pages

When to open — Washington When to close — Washington All states →