Michigan Pool Season: Opening & Closing Dates by City

Local dates for every featured Michigan city — when the water warms up, when it cools off, and how long the season actually lasts.

City Opening window Closing window Season
Detroit May 23 – Jun 10 Sep 3 – Sep 23 ≈ 107 days
Grand Rapids May 29 – Jun 20 Aug 21 – Sep 15 ≈ 87 days
Traverse City Jun 9 – Jul 10 Aug 4 – Sep 7 ≈ 65 days
Marquette Jun 28 – Jul 10 Aug 21 – Sep 3 ≈ 41 days

Windows show the stretch when each city's daily average passes through the low-to-mid 60s°F (1991–2020 NOAA records, nearest station to each city). Click a city for its month-by-month table and full season notes.

Season geography

Across Michigan's featured cities, typical openings spread from Jun 1 to Jul 10, closings from Aug 21 to Sep 15, and the unheated season runs 41–107 days depending on where you are. Elevation, coastal water, and urban heat all pull real dates around, which is exactly why a state-level answer isn't enough.

For your exact town, the pool season lookup takes a ZIP code. Opening day itself is a chemistry job — the dosing calculator turns your first test reading of the year into exact amounts.

Michigan planning pages

When to open — Michigan When to close — Michigan All states →