Pool closing · Colorado
When to Close Your Pool in Colorado Springs, CO: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Plan to close your Colorado Springs pool by October 1. The local 7-day mean temperature drops out of the algae-risk zone around September 21, and NOAA normals put the first 32°F freeze near October 8 — winterize between those dates and the water goes under the cover cold, clean, and easy to reopen. Below: today's water estimate, the full closing window, and a step-by-step winterizing checklist.
Colorado Springs closing dates at a glance
| Closing window | September 21 – October 1 |
|---|---|
| Close by (deadline) | October 1 |
| First freeze, 50% probability | October 8 |
| Open by (recommended) | May 13 |
| Opening window | May 6 – May 27 |
| 61°F crossing (7-day mean) | May 27 |
| Swim-season length (80°F+ days) | 90 days |
| NOAA normals station | Colorado Springs Municipal Airport · 5.5 mi · 6181 ft |
A short season cuts both ways: every week opened before May 27 is a real slice of Colorado Springs's roughly 90-day warm-swim budget.
At roughly 6181 ft, Colorado Springs Municipal Airport runs cooler than lowland forecasts for the same region — trust these local numbers over metro-wide weather graphics.
The same model in water terms: Colorado Springs's estimated pool temperature runs about 46°F in mid-April, 66°F in mid-June, 71°F in mid-August, and 54°F in mid-October, peaking near 72°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.
The 12-step Colorado Springs 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
Do the chemistry midweek, close on the weekend: alkalinity and pH into label ranges with days of circulation left to spread them. Winter locks in whatever state the water holds on closing day.
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Deep-clean the pool
Make the last cleaning the best one of the year: full skim, full brush, careful vacuum. Debris left behind steeps all winter and greets you as April's water problem.
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Service the filter one last time
Send the filter into winter clean: backwash the sand or DE, rinse and dry the cartridges indoors. Media stored dirty over winter hardens into a spring problem no backwash fixes.
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Apply winter chemicals per label
Run the winter kit through moving water: dose each product per its label with the pump on, give it a few hours to distribute, then start the shutdown. Chemistry added to still water stays where it lands.
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Lower the water level
Drop the level as your cover manufacturer specifies — typically below the skimmer mouth for solid covers. Never drain a pool fully; groundwater pressure can damage the shell.
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Blow out the lines and plug returns
The blowout is the whole ballgame: drive air through each line until it runs dry, seat the plug against the airflow, move to the next. A dry line cannot burst, full stop.
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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
If any line can't be verified dry, add pool-grade antifreeze per its label. Use only pool antifreeze — automotive products don't belong in pool plumbing.
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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
Float a centered air pillow, then land the cover and secure it the way its design intends — bags, cable, or straps. Ice sheets need somewhere to collapse inward, and the pillow is that somewhere.
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Note this year's dates
Jot down when Colorado Springs's water actually cooled and when you closed. A two-line note beats memory next September 21 — your own yard runs a few days off any model, including ours.
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Remove and store ladders and rails
Pull ladders, rails, and the diving-board hardware; rinse, dry, and store them out of the weather. Anchor sockets get a dab of protectant so spring bolts turn freely.
What to buy before the rush
Every item below sells out somewhere in Colorado every September. Stocking the short list before the rush costs nothing extra and saves the mid-project store run — the chemicals guide explains what each category actually does.
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Winter cover
Measure with overlap; the winter workhorse over everything else.
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Cover pump
Keeps rain and melt off a solid cover all season.
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Expansion plugs + skimmer guard
Cheap rubber that stands between ice and your fittings.
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Pool antifreeze
For lines you can't verify dry — pool-grade only, per label.
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Winter closing kit
Season-length winter chemicals in one label-dosed box.
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Air pillow
Gives ice somewhere to push besides your pool walls.
How Colorado Springs compares locally
Two nearby data points to triangulate with: Castle Rock, 36 miles from Colorado Springs, models its close at September 25 (about a week earlier); Pueblo, 42 miles out, at October 2. Colorado Springs's own window ends October 1. For the other half of the calendar see when to open in Colorado Springs, or scan the full year on the season page.
Local means local: Colorado Springs's dates come from Colorado Springs Municipal Airport, the nearest station with complete daily temperature normals — 5.5 miles southeast, about 6181 feet up. Between that station and a El Paso County backyard there's always a degree or two of microclimate; the windows are built wide enough to carry it.
Field notes for Colorado Springs owners
Gas heaters get the manual, not a guess
Every heater brand sequences its winterizing differently — drain plugs, blower considerations, gas supply, control settings. The generic advice (drain fully, close the valve) is right but incomplete; ten minutes with your model's manual protects the most expensive component you'll winterize.
What comes indoors
Cartridges, the cover pump when idle, chemical containers, and anything with a small motor overwinter better in the garage. Cold cycling is hard on plastics and seals; shelf space is cheaper than replacements. Label a single bin now and spring assembly becomes a scavenger hunt with a map.
The mesh-cover spring surprise, prevented in fall
Mesh-covered pools green up early because late-winter sun plus nutrient-carrying meltwater reaches the water. The fall counter-moves: close late and cold, dose the winter kit exactly per label, and plan an early-spring peek under the cover rather than a Memorial Day reveal.
Closing for a real winter
A Colorado Springs closing has to hold for months of freeze-thaw, not a few frosty mornings. Spend the effort where winters bite: prove every line dry, drain every vessel on the pad, guard the skimmer, and tension the cover for wind that will actually come. The reward is a spring opening that's a rinse, not a rebuild.
Closing at 6181 feet
High-elevation autumns lie: Colorado Springs afternoons can feel like swim weather the same week a clear night dips below 32°F. The defense is preparation — blowout gear staged early, the October 8 freeze normal taken literally, and any dry cold front in October treated as the starting gun rather than a curiosity.
Colorado Springs 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 Colorado Springs's actual water; the normals say the durable cool-down arrives near September 21, and anything inside the window to October 1 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. Colorado Springs's water doesn't settle below the risk zone until around September 21 — closing much before that trades a few weekends of maintenance for a rough spring.
Do I need antifreeze in pool lines?
Only for lines you can't verify dry — a proper blowout makes antifreeze unnecessary. Where doubt remains, use pool-grade product at its label rate, never automotive. No freeze-probability normal is published near Colorado Springs, so let the live forecast, not a calendar, tell you when freeze protection starts mattering.
How far should I drain my pool for winter?
Follow the cover's instructions first: solid covers usually want water a few inches below the skimmer; some mesh setups run higher with the skimmer sealed. The hard rule is never empty — hydrostatic pressure can lift or crack an empty pool, a far worse outcome than any freeze.
What happens if you don't winterize a pool?
The freeze finds every shortcut. Ice in an unprotected pump or heater cracks castings from the inside; ice in underground lines splits fittings you can't see until spring. Colorado Springs reaches freeze territory around October 8 — the checklist above is cheaper than any one of those repairs.
When is the last safe date to close in Colorado Springs?
Our model's practical deadline is October 1 — set by a week of margin before the October 8 first-freeze normal. Push much past it and you're winterizing in freeze-warning weather, rushing the blowout, and hoping the cover goes on before the first hard night. Inside the September 21–October 1 window, none of that drama applies.
Email me when Colorado Springs hits the closing window
Data: NOAA 1991–2020 climate normals via Colorado Springs Municipal Airport (5.5 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.