Pool season · Montana
Billings Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Billings pool. The season bar below draws everything the model knows — opening window, prime season, closing window — against today's date, with the working details one click away on the opening and closing pages.
Billings, MT — 72 swim days a yearThe bar compresses Billings's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the May 13–June 3 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends September 27. Wherever the today marker sits, the nearest color change is your next appointment.
The Billings pool calendar
Opening — target May 20
Open by May 20 — a two-week head start on the June 3 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 27
The window opens September 17 once water leaves the algae zone; the model deadline is September 27, a week ahead of the October 7 freeze normal.
Estimated water temperature by month
This is Billings's typical-year water curve: the same EWMA model as the live widget, run on the 1991–2020 normals instead of this week's weather.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 27° | 28° | 34° | 43° | 51° | 61° | 70° | 74° | 67° | 55° | 41° | 31° |
The curve peaks near 75°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Missoula's pool season or jump back to the Montana season index to see the statewide spread.
Billings pool season FAQ
When should I open my pool in Billings, MT?
Open by May 20 — the model places Billings's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Billings opening guide has the 12-step sequence.
When should I close my pool in Billings?
Close by September 27: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Billings closing guide sequences the work backward from that date.
How long is the swim season in Billings?
Billings averages 72 days a year with normal highs of 80°F or better — about 18 days earlier than the Montana median. The Montana season index ranks all 2 covered cities by the same metric.
How warm does pool water get in Billings?
An unheated pool near Billings typically peaks around 75°F in high summer and bottoms out near 27°F in winter, never quite reaching the 78°F comfort line without a heater or solar cover. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when Billings hits the closing window
Data: NOAA 1991–2020 climate normals via Billings Logan International Airport (1.3 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.