Pool closing · State guide
When to Close Your Pool in Michigan
Last updated: July 15, 2026 · 23 cities covered
Closing deadlines across Michigan stretch about 8 days: Flint needs the cover on first (September 28), Detroit last (October 6), and the statewide median deadline is October 1.
Each deadline is the model's two-clock compromise — ten days after the water leaves the algae zone, capped a week before the local 50% first-freeze date. City pages carry the live widget that flags early-freeze years and the full winterizing sequence.
| City | Window opens | Close by | First freeze (50%) |
|---|---|---|---|
| Ann Arbor | Sep 19 | Sep 29 | Oct 10 |
| Battle Creek | Sep 22 | Oct 2 | Oct 19 |
| Dearborn | Sep 24 | Oct 4 | Oct 15 |
| Detroit | Sep 26 | Oct 6 | Oct 25 |
| Farmington Hills | Sep 19 | Sep 29 | Oct 17 |
| Flint | Sep 18 | Sep 28 | Oct 13 |
| Grand Rapids | Sep 19 | Sep 29 | Oct 10 |
| Holland | Sep 21 | Oct 1 | Oct 21 |
| Jackson | Sep 20 | Sep 30 | Oct 14 |
| Kalamazoo | Sep 22 | Oct 2 | Oct 18 |
| Lansing | Sep 20 | Sep 30 | Oct 13 |
| Livonia | Sep 19 | Sep 29 | Oct 17 |
| Muskegon | Sep 22 | Oct 2 | Oct 19 |
| Port Huron | Sep 26 | Oct 6 | Nov 3 |
| Rochester Hills | Sep 23 | Oct 3 | Oct 22 |
| Saginaw | Sep 21 | Oct 1 | Oct 21 |
| South Lyon | Sep 18 | Sep 28 | Oct 13 |
| Southfield | Sep 19 | Sep 29 | Oct 17 |
| Sterling Heights | Sep 21 | Oct 1 | Oct 24 |
| Troy | Sep 23 | Oct 3 | Oct 22 |
| Warren | Sep 26 | Oct 6 | Oct 31 |
| Westland | Sep 25 | Oct 5 | Oct 27 |
| Wyoming | Sep 19 | Sep 29 | Oct 10 |
Dates are typical-year model outputs, not forecasts — each city guide carries the live widget that tracks the current year against them.
How to use these dates
Each "close by" deadline is the model's two-clock compromise for that city: ten days after its 7-day mean temperature falls back through 61°F (water goes algae-dormant soon after), but never later than a week before its 50% first-freeze date from the NOAA 1991–2020 normals. Closing inside the window seals cold, stable water under the cover; closing early seals a warm algae incubator instead.
Treat the dates as typical-year guidance, not forecasts. An early cold snap moves the real deadline — each city guide runs a live water-temperature widget that flags a 32°F night inside the 10-day forecast as urgent, and carries the full winterizing checklist in working order.