Pool season · District of Columbia
Washington Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Washington pool. The season bar below draws everything the model knows — opening window, prime season, closing window — against today's date, with the working details one click away on the opening and closing pages.
Washington, DC — 115 swim days a yearEach dot on the bar is one week of Washington's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (April 6–April 27), solid teal is swim season, and hollow amber is the closing window ending October 21. The black marker is today — its position against the colors is the entire executive summary.
The Washington pool calendar
Opening — target April 13
Open by April 13 — a two-week head start on the April 27 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 21
The window opens October 11 once water leaves the algae zone; the model deadline is October 21, a week ahead of the November 8 freeze normal.
Estimated water temperature by month
This is Washington's typical-year water curve: the same EWMA model as the live widget, run on the 1991–2020 normals instead of this week's weather.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 38° | 37° | 42° | 52° | 63° | 72° | 79° | 80° | 76° | 65° | 54° | 44° |
Warmest water typically July–August (peaking near 80°F); heaters and covers shift any month up.
Washington pool season FAQ
When should I open my pool in Washington, DC?
Target April 13. That date backs off two weeks from the day Washington's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the Washington opening guide.
When should I close my pool in Washington?
The closing deadline is October 21 — late enough that the water has cooled out of the algae zone, early enough to beat Washington's first-freeze normal by about a week. See the Washington closing guide for the winterizing steps.
How long is the swim season in Washington?
Washington averages 115 days a year with normal highs of 80°F or better — right on the statewide median. The District of Columbia season index ranks all 1 covered cities by the same metric.
How warm does pool water get in Washington?
An unheated pool near Washington typically peaks around 80°F in high summer and bottoms out near 36°F in winter, spending roughly 2 months at or above the 78°F comfort line most swimmers prefer. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when Washington hits the closing window
Data: NOAA 1991–2020 climate normals via National Arboretum Dc (2.5 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.