Pool season · California
Sunnyvale Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Sunnyvale'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.
Sunnyvale, CA — 0 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Sunnyvale's swim season; the hollow teal run before it (April 16 to May 7) is when to open; the hollow amber run after is when to close, with November 7 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Sunnyvale pool calendar
Opening — target April 23
Open by April 23 — a two-week head start on the May 7 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline November 7
Hold the cover until October 28, then winterize by November 7, a week ahead of the December 23 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Sunnyvale'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 50° | 52° | 55° | 57° | 60° | 64° | 67° | 68° | 68° | 66° | 60° | 52° |
The curve peaks near 68°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Stockton's pool season and Temecula's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the California season index.
Sunnyvale pool season FAQ
When should I open my pool in Sunnyvale, CA?
Open by April 23 — the model places Sunnyvale's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Sunnyvale opening guide has the 12-step sequence.
When should I close my pool in Sunnyvale?
Close by November 7: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Sunnyvale closing guide sequences the work backward from that date.
How long is the swim season in Sunnyvale?
Sunnyvale averages 0 days a year with normal highs of 80°F or better — about 22 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 Sunnyvale?
An unheated pool near Sunnyvale typically peaks around 68°F in high summer and bottoms out near 50°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 Sunnyvale hits the closing window
Data: NOAA 1991–2020 climate normals via Moffett Federal Airfield (2.0 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.