Pool season · Colorado
Castle Rock Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
One bar, one year, one Castle Rock 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.
Each dot on the bar is one week of Castle Rock's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (May 12–June 2), solid teal is swim season, and hollow amber is the closing window ending September 25. The black marker is today — its position against the colors is the entire executive summary.
The Castle Rock pool calendar
Opening — target May 19
Target May 19; the practical window runs May 12–June 2, and the 7-day mean crosses the 61°F threshold around June 2. Cold-water starts are the cheap ones.
Closing — deadline September 25
Hold the cover until September 17, then winterize by September 25, a week ahead of the October 2 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Castle Rock's own normals — the shape of a typical year, not a forecast. The widget above shows where the current year actually sits.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 32° | 32° | 37° | 43° | 50° | 61° | 69° | 71° | 66° | 55° | 44° | 35° |
The curve peaks near 71°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Castle Rock hits the closing window
Data: NOAA 1991–2020 climate normals via Castle Rock (3.7 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.