Pool season · California
Westminster Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Westminster 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.
Westminster, CA — 105 swim days a yearEach dot on the bar is one week of Westminster's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (February 16–March 9), solid teal is swim season, and hollow amber is the closing window ending December 4. The black marker is today — its position against the colors is the entire executive summary.
The Westminster pool calendar
Opening — target February 23
Open by February 23 — a two-week head start on the March 9 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline December 4
Hold the cover until November 24, then winterize by December 4, a week ahead of the December 25 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Westminster'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 59° | 59° | 60° | 63° | 65° | 68° | 72° | 74° | 75° | 72° | 67° | 60° |
The curve peaks near 75°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with West Covina's pool season and Whittier's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the California season index.
Westminster pool season FAQ
When should I open my pool in Westminster, CA?
Target February 23. That date backs off two weeks from the day Westminster's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the Westminster opening guide.
When should I close my pool in Westminster?
The closing deadline is December 4 — late enough that the water has cooled out of the algae zone, early enough to beat Westminster's first-freeze normal by about a week. See the Westminster closing guide for the winterizing steps.
How long is the swim season in Westminster?
Westminster averages 105 days a year with normal highs of 80°F or better — about 37 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 Westminster?
An unheated pool near Westminster typically peaks around 75°F in high summer and bottoms out near 58°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 Westminster hits the closing window
Data: NOAA 1991–2020 climate normals via Santa Ana Fire Station (7.3 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.