Pool opening · Wyoming
When to Open Your Pool in Cheyenne, WY: Best Dates & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
The Cheyenne answer is May 28 — open then, and the water is still weeks shy of the algae zone it enters after June 11. You get a cheap, clean startup and first pick of chemicals and service slots. Below: the live water estimate for today, the exact window, and the checklist that turns it into one weekend of work.
Cheyenne opening dates at a glance
| Open by (recommended) | May 28 |
|---|---|
| Opening window | May 21 – June 11 |
| 61°F crossing (7-day mean) | June 11 |
| Closing window | September 10 – September 20 |
| Close by (deadline) | September 20 |
| First freeze, 50% probability | October 1 |
| Swim-season length (80°F+ days) | 58 days |
| NOAA normals station | Cheyenne Wfo · 1.4 mi · 6119 ft |
A short season cuts both ways: every week opened before June 11 is a real slice of Cheyenne's roughly 58-day warm-swim budget.
Elevation caveat: Cheyenne's station sits near 6119 ft, where clear-night cooling outpaces valley forecasts; the local normals above already reflect that.
Four water checkpoints anchor Cheyenne's year in the model: mid-April at about 41°F, mid-June at 61°F, mid-August near the 68°F peak zone, and mid-October easing through 49°F. The dates in the table are where those numbers cross the thresholds that matter.
The 12-step Cheyenne opening checklist
Sequenced for a May 21–June 11 window: the first five steps are one honest afternoon, the middle is a 24-hour pump run, and the rest is testing patience. Chemical steps always defer to the product label; the un-dated generic version of this sequence lives in the how-to guide.
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Pump off and clear the winter cover
Drain standing water with a cover pump, sweep off debris, then drag the cover clear without dumping the muck into the pool. Working backward from May 28 means doing this while mornings are still cool.
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Top up the water level
Bring the level up to the middle of the skimmer opening before anything runs. Too low and the pump gulps air; too high and the skimmer door stops doing its job.
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Remove winter plugs and reinstall fittings
Swap winter hardware for summer hardware: plugs out, eyeballs and baskets in, ladders re-anchored. Bag the winter plugs and label the bag; fall-you will hunt for them otherwise.
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Reassemble the equipment pad
Reinstall drain plugs on the pump, filter, and heater; lube o-rings with the manufacturer-recommended lubricant; reconnect unions hand-tight plus a quarter turn.
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Prime the pump and run for 24 hours
Pour water into the pump housing, crack the filter's air relief, and fire it up. Give the system a continuous day of runtime before you draw any conclusions about the water.
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Service the filter
Whatever the media — cartridge, sand, or DE — start the season with it clean, following the manual's procedure. A half-clogged filter turns a two-day clearing into a week.
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Brush, skim, and vacuum
Sweep the whole shell — walls, steps, floor — then skim and vacuum what you raised. Removing solids mechanically is the cheapest chemical treatment there is, because it isn't one.
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Test the water
Get a real baseline before spending a dollar on chemicals: full-panel test with fresh reagents. Winter reliably moves pH, alkalinity, and stabilizer, and guessing at any of them costs more than the strips do.
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Balance, then shock — per product labels
Adjust alkalinity first, then pH, following each product's label dosing for your pool volume. Once balanced, apply a startup shock as its label directs and run the pump overnight.
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Filter until the water clears
Keep the pump on long cycles and re-test each day until clarity arrives and the numbers stop moving. Cold-water openings usually polish out fast; procrastinated ones pay in filter-hours.
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Inspect for winter damage
Walk the deck, coping, and tile line looking for new cracks, and watch the pad for drips during the first day of runtime. Catching a weep in May 21 beats a leak hunt in June.
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Rinse the surrounds before first swim
Hose pollen and winter grit off the deck and furniture so the first windy day doesn't dump it straight back into clean water. A skimmer sock helps through peak pollen weeks.
What to buy before the rush
A small stack of supplies turns the checklist above into a single-weekend job. Buy before Cheyenne's June rush and the whole list ships at leisure instead of sprinting.
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7-way test strips
The first thing to run and the last thing to skimp on.
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Start-up shock
The opening oxidizer; dose by the label for your volume.
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Filter cartridge / DE refill
Swap or refresh at opening while everything is already apart.
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Leaf net + wall brush
Wall brush plus deep net — the manual half of every checklist.
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Robotic pool cleaner
Hands-off floor and wall cleaning while you do the chemistry.
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Pool opening chemical kit
One box covers balancing and startup for most residential volumes.
How Cheyenne compares locally
Cheyenne sits in the earlier half of Wyoming's pool calendar — about 50% of the 1 Wyoming cities we model open earlier. The nearest checkpoints agree: Fort Collins (43 mi away) models to May 12 (roughly two weeks earlier), and Greeley (50 mi) to May 6. Planning the other end of the year? The mirror guide covers closing in Cheyenne, and the season overview puts both windows on one bar.
The measuring stick here is Cheyenne Wfo — 1.4 miles to the northwest, elevation about 6119 feet. Its 1991–2020 record is what the model reads for Cheyenne; your backyard in Laramie County will run a touch warmer or cooler with shade, wind, and pavement, which is exactly the slack the two-week lead absorbs.
Field notes for Cheyenne owners
Why a cold start is a cheap start
Every degree below the algae threshold at opening day is money: cold water lets a modest, label-dosed shock establish sanitizer residual before anything grows, and the filter spends its hours polishing instead of fighting. The same pool opened three weeks later often needs multiple treatments to reach the identical end state.
Salt pools: check the cell before the season leans on it
Opening is the natural moment to inspect a salt cell: scale on the plates, connections, and the salinity reading after fresh spring water. Follow the manufacturer's cleaning guidance exactly — over-acid-washing a cell shortens its life more than the scale did. The salt-water opening notes cover the cold-water handoff too.
The service-rush arithmetic
Pool service calendars fill in reverse: the crews that install liners and fix heaters in April are fully booked by the first hot weekend. Opening early means any problem you discover — a seeping seal, a dead capacitor — gets an appointment this month, not after Memorial Day. Weighing hired help against a Saturday? The service-vs-DIY guide breaks down what a visit includes.
Opening at 6119 feet
Elevation gives Cheyenne a split personality in spring: strong afternoon sun over water that clear nights keep re-chilling. Work with it — the UV argues for testing stabilizer early, the cold nights argue for a solar cover, and the honest signal for timing is the weekly mean, never one warm deck-lunch of an afternoon.
Short-season strategy
Cheyenne gets about 58 days of 80°F-plus afternoons in the normals — a season measured in weekends. Opening by May 28 converts otherwise-lost spring weeks into usable shoulder season, and a solar cover stretches both ends. In short-summer country, the calendar is the most valuable pool equipment you own.
Cheyenne pool opening FAQ
What water temperature causes pool algae?
Roughly 65°F is where algae shift from dormant to hungry, and growth keeps speeding up as water warms toward the 80s. Cold water is your ally: open while Cheyenne's water is still cool — the model crossing lands around June 11 — and sanitizer establishes control before biology gets a vote.
What temperature should it be outside to open a pool?
Think in weekly averages, not single sunny days. Once the 7-day mean temperature reaches the low 60s°F — June 11 in Cheyenne, per NOAA normals — water warms into algae territory within days. A 70°F-afternoon stretch is the same signal read off a thermometer instead of a dataset.
Is it cheaper to open a pool early or late?
Late openings look cheaper on the calendar and cost more at the register. Once water sits above the algae threshold under a cover — past June 11 here — the odds of opening green climb fast, and clearing a green pool multiplies chemical use and filter hours. Early water is cold, clean, and inexpensive.
How long after opening can you swim?
There's no fixed clock — it's a checklist. Clear water, stable readings inside the ranges your product labels specify, and any waiting period those labels state after shocking. Budget a couple of days after a tidy opening, longer if the pool wintered poorly.
What chemicals do I need to open a pool?
A test kit or strips, alkalinity and pH adjusters, calcium hardness increaser if your water runs soft, stabilizer (cyanuric acid), your regular sanitizer, and a startup shock. Buy before Cheyenne's rush around June 11, and dose everything strictly by each product's label for your pool volume — category-by-category buying notes live in the opening chemicals guide.
When do most people open pools in WY?
Nationally, early-to-mid May and the Memorial Day weekend dominate — which is why late openers meet empty shelves and week-long service waits. Our Wyoming model medians out at May 28 across 1 cities, and Cheyenne pencils in May 28, comfortably ahead of the rush.
Email me when Cheyenne hits the opening window
Data: NOAA 1991–2020 climate normals via Cheyenne Wfo (1.4 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.