Pool closing · State guide
When to Close Your Pool in Wyoming
Last updated: July 15, 2026 · 1 cities covered
Closing deadlines across Wyoming stretch about 0 days: Cheyenne needs the cover on first (September 20), Cheyenne last (September 20), and the statewide median deadline is September 20.
Each deadline is the model's two-clock compromise — ten days after the water leaves the algae zone, capped a week before the local 50% first-freeze date. City pages carry the live widget that flags early-freeze years and the full winterizing sequence.
| City | Window opens | Close by | First freeze (50%) |
|---|---|---|---|
| Cheyenne | Sep 10 | Sep 20 | Oct 1 |
Dates are typical-year model outputs, not forecasts — each city guide carries the live widget that tracks the current year against them.
How to use these dates
Each "close by" deadline is the model's two-clock compromise for that city: ten days after its 7-day mean temperature falls back through 61°F (water goes algae-dormant soon after), but never later than a week before its 50% first-freeze date from the NOAA 1991–2020 normals. Closing inside the window seals cold, stable water under the cover; closing early seals a warm algae incubator instead.
Treat the dates as typical-year guidance, not forecasts. An early cold snap moves the real deadline — each city guide runs a live water-temperature widget that flags a 32°F night inside the 10-day forecast as urgent, and carries the full winterizing checklist in working order.