Pool season · Wisconsin
Green Bay Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Green Bay 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.
Green Bay, WI — 14 swim days a yearEach dot on the bar is one week of Green Bay's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (May 11–June 1), solid teal is swim season, and hollow amber is the closing window ending September 23. The black marker is today — its position against the colors is the entire executive summary.
The Green Bay pool calendar
Opening — target May 18
Open by May 18 — a two-week head start on the June 1 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 23
Hold the cover until September 13, then winterize by September 23, a week ahead of the October 9 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Green Bay'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 19° | 17° | 26° | 38° | 50° | 61° | 68° | 69° | 64° | 54° | 42° | 29° |
The curve peaks near 70°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Eau Claire's pool season and Kenosha's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Wisconsin season index.
Green Bay pool season FAQ
When should I open my pool in Green Bay, WI?
Open by May 18 — the model places Green Bay's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Green Bay opening guide has the 12-step sequence.
When should I close my pool in Green Bay?
Close by September 23: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Green Bay closing guide sequences the work backward from that date.
How long is the swim season in Green Bay?
Green Bay averages 14 days a year with normal highs of 80°F or better — about 5 days later than the Wisconsin median. The Wisconsin season index ranks all 11 covered cities by the same metric.
How warm does pool water get in Green Bay?
An unheated pool near Green Bay typically peaks around 70°F in high summer and bottoms out near 16°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 Green Bay hits the closing window
Data: NOAA 1991–2020 climate normals via Green Bay Botanical (5.5 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.