Pool season · California
Modesto Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Modesto'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.
Modesto, CA — 159 swim days a yearEach dot on the bar is one week of Modesto'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 26–April 16), solid teal is swim season, and hollow amber is the closing window ending November 7. The black marker is today — its position against the colors is the entire executive summary.
The Modesto pool calendar
Opening — target April 2
Target April 2; the practical window runs March 26–April 16, and the 7-day mean crosses the 61°F threshold around April 16. Cold-water starts are the cheap ones.
Closing — deadline November 7
Hold the cover until October 28, then winterize by November 7, a week ahead of the December 5 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Modesto'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 47° | 50° | 55° | 59° | 65° | 72° | 77° | 79° | 76° | 70° | 60° | 50° |
Warmest water typically August–August (peaking near 79°F); heaters and covers shift any month up.
Every station tells its own story: compare this curve with Mission Viejo's pool season and Moreno Valley's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the California season index.
Modesto pool season FAQ
When should I open my pool in Modesto, CA?
The site model recommends opening by April 2 — about two weeks before Modesto'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 Modesto opening guide.
When should I close my pool in Modesto?
Winterize by November 7. The model holds the deadline a week ahead of Modesto's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Modesto closing guide.
How long is the swim season in Modesto?
Modesto averages 159 days a year with normal highs of 80°F or better — right on the statewide median. The California season index ranks all 147 covered cities by the same metric.
How warm does pool water get in Modesto?
An unheated pool near Modesto typically peaks around 79°F in high summer and bottoms out near 47°F in winter, spending roughly 1 month 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 Modesto hits the closing window
Data: NOAA 1991–2020 climate normals via Modesto City Co Airport (3.0 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.