Pool season · Wisconsin
Wausau Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Wausau'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.
Wausau, WI — 26 swim days a yearEach dot on the bar is one week of Wausau'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 10–May 31), solid teal is swim season, and hollow amber is the closing window ending September 21. The black marker is today — its position against the colors is the entire executive summary.
The Wausau pool calendar
Opening — target May 17
Open by May 17 — a two-week head start on the May 31 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 21
The window opens September 11 once water leaves the algae zone; the model deadline is September 21, a week ahead of the October 4 freeze normal.
Estimated water temperature by month
Monthly averages of the site's water model run on Wausau'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 17° | 16° | 25° | 37° | 50° | 62° | 68° | 69° | 64° | 53° | 39° | 26° |
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 Sheboygan's pool season and Appleton's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Wisconsin season index.
Wausau pool season FAQ
When should I open my pool in Wausau, WI?
The site model recommends opening by May 17 — about two weeks before Wausau'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 Wausau opening guide.
When should I close my pool in Wausau?
Winterize by September 21. The model holds the deadline a week ahead of Wausau's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Wausau closing guide.
How long is the swim season in Wausau?
Wausau averages 26 days a year with normal highs of 80°F or better — about 4 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 Wausau?
An unheated pool near Wausau typically peaks around 70°F in high summer and bottoms out near 14°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 Wausau hits the closing window
Data: NOAA 1991–2020 climate normals via Wausau Dwtn Airport (2.7 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.