Pool season · California
San Ramon Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
San Ramon'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.
San Ramon, CA — 81 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is San Ramon's swim season; the hollow teal run before it (May 8 to May 29) is when to open; the hollow amber run after is when to close, with November 1 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The San Ramon pool calendar
Opening — target May 15
Open by May 15 — a two-week head start on the May 29 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline November 1
Hold the cover until October 22, then winterize by November 1, a week ahead of the December 22 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is San Ramon'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° | 48° | 49° | 52° | 56° | 62° | 70° | 72° | 71° | 67° | 58° | 49° |
The curve peaks near 72°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with San Mateo's pool season and Santa Ana's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the California season index.
San Ramon pool season FAQ
When should I open my pool in San Ramon, CA?
Open by May 15 — the model places San Ramon's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The San Ramon opening guide has the 12-step sequence.
When should I close my pool in San Ramon?
Close by November 1: cool water keeps its winter chemistry, but freeze damage is the hard stop. The San Ramon closing guide sequences the work backward from that date.
How long is the swim season in San Ramon?
San Ramon averages 81 days a year with normal highs of 80°F or better — about 44 days later than the California median. The California season index ranks all 147 covered cities by the same metric.
How warm does pool water get in San Ramon?
An unheated pool near San Ramon typically peaks around 72°F in high summer and bottoms out near 47°F in winter, never quite reaching the 78°F comfort line without a heater or solar cover. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when San Ramon hits the closing window
Data: NOAA 1991–2020 climate normals via Mt Diablo Junction (8.1 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.