Pool season · California
Rialto Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Rialto's whole pool calendar, condensed: when the water warms, when it cools, and where today falls between those edges. Use the opening guide and closing guide for the step-by-step work; keep this page for the dates.
Rialto, CA — 162 swim days a yearEach dot on the bar is one week of Rialto's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (March 14–April 4), solid teal is swim season, and hollow amber is the closing window ending November 28. The black marker is today — its position against the colors is the entire executive summary.
The Rialto pool calendar
Opening — target March 21
Open by March 21 — a two-week head start on the April 4 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 January 2 freeze normal.
Estimated water temperature by month
Monthly averages of the site's water model run on Rialto'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° | 57° | 58° | 61° | 65° | 70° | 76° | 80° | 79° | 72° | 65° | 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 Redwood City's pool season and Richmond's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the California season index.
Rialto pool season FAQ
When should I open my pool in Rialto, CA?
Open by March 21 — the model places Rialto's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Rialto opening guide has the 12-step sequence.
When should I close my pool in Rialto?
Close by November 28: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Rialto closing guide sequences the work backward from that date.
How long is the swim season in Rialto?
Rialto averages 162 days a year with normal highs of 80°F or better — about 11 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 Rialto?
An unheated pool near Rialto typically peaks around 80°F in high summer and bottoms out near 56°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 Rialto hits the closing window
Data: NOAA 1991–2020 climate normals via Riverside Citrus Experiment (10.5 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.