Pool season · California
Rancho Cucamonga Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
This is the one-page view of Rancho Cucamonga's pool year: both model windows, the estimated water-temperature curve, and today's live position on the season bar. The detailed checklists live on the opening and closing guides; this page is the calendar you check between them.
The bar compresses Rancho Cucamonga's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the March 4–March 25 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends November 28. Wherever the today marker sits, the nearest color change is your next appointment.
The Rancho Cucamonga pool calendar
Opening — target March 11
Target March 11; the practical window runs March 4–March 25, and the 7-day mean crosses the 61°F threshold around March 25. Cold-water starts are the cheap ones.
Closing — deadline November 28
The window opens November 18 once water leaves the algae zone; the model deadline is November 28, a week ahead of the December 30 freeze normal.
Estimated water temperature by month
This is Rancho Cucamonga'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 56° | 56° | 59° | 62° | 66° | 70° | 77° | 80° | 80° | 74° | 66° | 58° |
Warmest water typically August–September (peaking near 80°F); heaters and covers shift any month up.
Email me when Rancho Cucamonga hits the closing window
Data: NOAA 1991–2020 climate normals via Ontario International Airport (5.1 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.