Pool closing · Utah
When to Close Your Pool in St. George, UT: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Target October 30 as the practical closing deadline in St. George. Our model of NOAA 1991–2020 normals keeps the 7-day mean above 61°F until October 20; after that, cooling water winds algae down while you work the checklist below. The hard stop is equipment freeze damage — normals put St. George's first 32°F night near November 10.
St. George closing dates at a glance
| Closing window | October 20 – October 30 |
|---|---|
| Close by (deadline) | October 30 |
| First freeze, 50% probability | November 10 |
| Open by (recommended) | April 5 |
| Opening window | March 29 – April 19 |
| 61°F crossing (7-day mean) | April 19 |
| Swim-season length (80°F+ days) | 164 days |
| NOAA normals station | St George · 3.4 mi · 2857 ft |
St. George's 164-day warm season leaves comfortable margins on both ends — the windows above aim you at the cheap-chemistry versions of each transition.
Put dates aside and follow the water: the St. George curve says roughly 59°F by mid-April, 79°F by mid-June, 86°F in mid-August, then back down through 66°F in mid-October. The summer ceiling sits near 87°F, and every window above is just a line drawn on this curve.
The 12-step St. George winterizing checklist
The order matters more than the date: balanced water first, verified-dry lines before anything else freezes-proofs, and the cover only after everything below it is done. Work the list inside the window above.
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Balance the water a few days ahead
Start midweek for a weekend close: bring alkalinity and pH into their label ranges and let the water settle. What you seal under the cover is what the pool soaks in until spring.
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Deep-clean the pool
Brush, skim, and vacuum like company's coming. A pool that goes under the cover spotless comes out needing a rinse; one that goes under dirty comes out needing a project.
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Service the filter one last time
Backwash sand or DE, or pull and rinse cartridges, per the manual. A filter stored dirty cakes over winter and starts spring half-clogged.
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Apply winter chemicals per label
Add a winterizing kit or your usual closing chemicals exactly as their labels direct for your volume, with the pump still circulating so everything distributes before shutdown.
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Lower the water level
Take the level down only as far as the cover's manual says — usually just below the skimmer for solid covers, higher for many mesh systems. An empty pool is never the goal; shells crack and shift without water's weight.
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Blow out the lines and plug returns
Push air through skimmer, return, and cleaner lines until they run dry mist, then seat expansion plugs at each return while air still flows. This is the single most important freeze-protection step.
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Protect the skimmer
Seat a skimmer guard or bottle in the throat — ice that forms there needs a sacrifice, and a two-dollar bottle beats a plumbing repair under the deck.
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Add pool antifreeze where blowouts fall short
Antifreeze is the insurance policy for doubtful lines, not a replacement for the blowout: pool-grade product, label dosing, and only where air couldn't finish the job.
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Drain the equipment
Open every drain plug on the pump, filter, heater, and chlorinator, and store the plugs in the pump basket so spring reassembly is a one-stop hunt. Move what you can indoors.
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Set the air pillow and cover
Pillow first, cover second, tension last. A properly centered pillow turns the winter ice sheet from a wall-pressing ram into a harmless dome.
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Calendar the off-season checks
Set a monthly reminder from October 30 to spring: check cover tension, pump off standing water, and glance at the water level. Fifteen minutes a month protects the whole closing job.
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Winterize the water features
Waterfalls, slides, and spillover spas hold water in places gravity won't clear — blow those lines separately and plug them, or they'll be the one crack you find in spring.
What to buy before the rush
A small stack of supplies turns the checklist above into a single-weekend job. Buy before St. George's October rush and the whole list ships at leisure instead of sprinting.
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Air pillow
Centers under the cover so ice pushes inward, not outward.
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Winter cover
Measure with overlap; the winter workhorse over everything else.
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Cover pump
Solid covers collect rain all winter; this is the drainage plan.
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Expansion plugs + skimmer guard
Seals blown-out lines and sacrifices itself to skimmer ice.
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Pool antifreeze
Backup for unverifiable lines; label rate per foot of pipe.
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Winter closing kit
Season-length winter chemicals in one label-dosed box.
How St. George compares locally
St. George closes in the earliest quarter of Utah's calendar. Neighbors run close: North Las Vegas (100 mi away) models its deadline at November 17 (roughly two weeks later vs St. George's October 30), while Sunrise Manor (103 mi) shows November 17. The spring mirror of this page is the St. George opening guide, and the season overview draws both windows on a single bar.
Local means local: St. George's dates come from St George, the nearest station with complete daily temperature normals — 3.4 miles northwest, about 2857 feet up. Between that station and a Washington County backyard there's always a degree or two of microclimate; the windows are built wide enough to carry it.
Field notes for St. George owners
Cover pumps die in the cold — plan for it
A cover pump left running into a hard freeze can lock in ice and burn out. On freezing forecasts, pull it, let the storm pass, and put it back for the melt. Automatic models with freeze protection earn their price in exactly one forgotten weekend.
Salt cells overwinter indoors
Remove the cell at closing, inspect and clean per the manufacturer, and store it inside with the unions capped. A dummy cell or spacer keeps the plumbing sealed. Cells left in outdoor plumbing through freezes are a common — and completely avoidable — spring casualty.
Leaf season vs closing day
If your yard drops serious leaves, the cheap trick is a leaf net over the main cover through the drop, then one bulk removal before snow. Leaves that winter on (or worse, under) the cover steep like tea and hand you stained water and clogged pumps in spring.
St. George pool closing FAQ
What temperature should water be to close a pool?
Cold enough that biology has clocked out — below 65°F and falling, ideally low 60s. The widget above tracks St. George's actual water; the normals say the durable cool-down arrives near October 20, and anything inside the window to October 30 closes clean.
Can you close a pool too early?
Absolutely. A pool closed warm is an algae incubator: no circulation, fading sanitizer, and weeks of growth-friendly temperatures. St. George's water doesn't settle below the risk zone until around October 20 — closing much before that trades a few weekends of maintenance for a rough spring.
Do I need antifreeze in pool lines?
Only where water might remain. If every line is properly blown out and plugged, air is the antifreeze. Lines you can't verify dry — long runs, low spots, water features — get pool-grade antifreeze dosed per its label. With St. George's first freeze normal near November 10, don't leave that question open.
How far should I drain my pool for winter?
As far as your cover manufacturer specifies and no farther — typically a few inches below the skimmer mouth for solid covers, near normal level for many mesh systems with skimmer plugs. Never drain fully: an empty shell can shift or crack under groundwater pressure.
What happens if you don't winterize a pool?
In a freeze climate, physics wins: water expands about 9% when it freezes, cracking pump housings, filter tanks, heat exchangers, and pipes. With St. George's first 32°F night arriving near November 10 in the normals, an unwinterized pad is a spring repair bill waiting to be discovered.
When is the last safe date to close in St. George?
Treat October 30 as the deadline in St. George. It's derived from the 1991–2020 normals: the cool-down plus ten days (the freeze normal, November 10, leaves room to spare). Weather varies year to year, so watch the 10-day forecast in late October — an early cold snap moves the real deadline, and the widget above flags exactly that.
Email me when St. George hits the closing window
Data: NOAA 1991–2020 climate normals via St George (3.4 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.