Pool season · Michigan
Ann Arbor Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
One bar, one year, one Ann Arbor 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.
The bar compresses Ann Arbor's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the May 4–May 25 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 Ann Arbor pool calendar
Opening — target May 11
Open by May 11 — a two-week head start on the May 25 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 10 freeze normal.
Estimated water temperature by month
This is Ann Arbor'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26° | 24° | 30° | 41° | 53° | 64° | 70° | 71° | 67° | 56° | 44° | 33° |
The curve peaks near 71°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Ann Arbor hits the closing window
Data: NOAA 1991–2020 climate normals via Ann Arbor SE (3.0 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.