Pool season · Wisconsin
Madison Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
This is the one-page view of Madison's pool year: both model windows, the estimated water-temperature curve, and today's live position on the season bar. The detailed checklists live on the opening and closing guides; this page is the calendar you check between them.
The bar compresses Madison's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the May 3–May 24 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends September 29. Wherever the today marker sits, the nearest color change is your next appointment.
The Madison pool calendar
Opening — target May 10
Open by May 10 — a two-week head start on the May 24 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 29
The window opens September 19 once water leaves the algae zone; the model deadline is September 29, a week ahead of the October 9 freeze normal.
Estimated water temperature by month
Monthly averages of the site's water model run on Madison'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 22° | 20° | 29° | 41° | 53° | 64° | 71° | 71° | 67° | 56° | 44° | 31° |
The curve peaks near 72°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Madison hits the closing window
Data: NOAA 1991–2020 climate normals via Uw Arboretum - Madison (3.4 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.