Pool season · California
Fontana Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Fontana 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.
Fontana, CA — 164 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Fontana's swim season; the hollow teal run before it (March 4 to March 25) is when to open; the hollow amber run after is when to close, with November 28 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Fontana pool calendar
Opening — target March 11
Open by March 11 — a two-week head start on the March 25 crossing keeps startup chemistry small and beats the local service rush.
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
Monthly averages of the site's water model run on Fontana'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 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 Folsom's pool season and Fremont's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the California season index.
Fontana pool season FAQ
When should I open my pool in Fontana, CA?
The site model recommends opening by March 11 — about two weeks before Fontana'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 Fontana opening guide.
When should I close my pool in Fontana?
Winterize by November 28. The model holds the deadline a week ahead of Fontana's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Fontana closing guide.
How long is the swim season in Fontana?
Fontana 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 Fontana?
An unheated pool near Fontana 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 Fontana hits the closing window
Data: NOAA 1991–2020 climate normals via Ontario International Airport (8.5 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.