Pool season · California
Rancho Cucamonga Pool Season: the Year on One Bar
Last updated: July 25, 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.
Rancho Cucamonga, CA — 164 swim days a yearThe 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.
Every station tells its own story: compare this curve with Rancho Cordova's pool season and Redding's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the California season index.
Rancho Cucamonga pool season FAQ
When should I open my pool in Rancho Cucamonga, CA?
The site model recommends opening by March 11 — about two weeks before Rancho Cucamonga's 7-day mean temperature crosses 61°F, while the water is still too cold for algae. The step-by-step sequence is in the Rancho Cucamonga opening guide.
When should I close my pool in Rancho Cucamonga?
Winterize by November 28. The model holds the deadline a week ahead of Rancho Cucamonga's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Rancho Cucamonga closing guide.
How long is the swim season in Rancho Cucamonga?
Rancho Cucamonga averages 164 days a year with normal highs of 80°F or better — about 21 days earlier than the California median. The California season index ranks all 147 covered cities by the same metric.
How warm does pool water get in Rancho Cucamonga?
An unheated pool near Rancho Cucamonga typically peaks around 80°F in high summer and bottoms out near 55°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 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.