District of Columbia Pool Season: Opening & Closing Dates by City

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

City Opening window Closing window Season
Washington Apr 28 – May 18 Sep 27 – Oct 12 ≈ 149 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

Washington sets the pace for District of Columbia: opening around May 8, closing around Oct 4, roughly 149 swimmable days. 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.

District of Columbia planning pages

When to open — District of Columbia When to close — District of Columbia All states →