Montana Pool Season: Opening & Closing Dates by City

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

City Opening window Closing window Season
Billings Jun 9 – Jul 2 Aug 21 – Sep 9 ≈ 71 days
Missoula Jun 22 – Jul 13 Aug 3 – Sep 3 ≈ 52 days
Great Falls Jun 13 – Jul 6 Aug 18 – Sep 5 ≈ 63 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 Montana's featured cities, typical openings spread from Jun 20 to Jul 2, closings from Aug 24 to Aug 30, and the unheated season runs 52–71 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.

Montana planning pages

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