Iowa Pool Season: Opening & Closing Dates by City

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

City Opening window Closing window Season
Des Moines May 14 – Jun 2 Sep 8 – Sep 25 ≈ 117 days
Cedar Rapids May 16 – Jun 5 Sep 3 – Sep 23 ≈ 112 days
Sioux City May 23 – Jun 9 Aug 31 – Sep 20 ≈ 103 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 Iowa's featured cities, typical openings spread from May 24 to Jun 1, closings from Sep 12 to Sep 18, and the unheated season runs 103–117 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.

Iowa planning pages

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