Colorado Pool Season: Opening & Closing Dates by City

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

City Opening window Closing window Season
Denver May 23 – Jun 8 Sep 9 – Sep 24 ≈ 110 days
Colorado Springs May 30 – Jun 20 Aug 25 – Sep 17 ≈ 90 days
Grand Junction May 11 – May 29 Sep 16 – Sep 29 ≈ 126 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 Colorado's featured cities, typical openings spread from May 20 to Jun 8, closings from Sep 6 to Sep 23, and the unheated season runs 90–126 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.

Colorado planning pages

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