When to Close Your Pool in Aurora, CO: Deadline, Window & Checklist

Aurora closing dates at a glance

Aurora's 105-day warm season leaves comfortable margins on both ends — the windows above aim you at the cheap-chemistry versions of each transition.

Elevation caveat: Aurora's station sits near 5647 ft, where clear-night cooling outpaces valley forecasts; the local normals above already reflect that.

The same model in water terms: Aurora's estimated pool temperature runs about 46°F in mid-April, 66°F in mid-June, 72°F in mid-August, and 54°F in mid-October, peaking near 74°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.

The 12-step Aurora winterizing checklist

Sequenced against Aurora's September 22–October 1 window: chemistry while the pump still runs, blowouts before the equipment drains, cover last. Labels dictate every dose.

1. Balance the water a few days ahead

   Give the chemistry a head start — balance to label ranges several days out, while circulation can still mix corrections evenly. Closing-day dosing never distributes as well.

2. 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.

3. 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.

4. Apply winter chemicals per label

   Dose the winter kit while the pump still runs — every product exactly per its label for your volume — so the chemistry is fully mixed before the system goes quiet.

5. Lower the water level

   Your cover's manual sets the number — commonly a few inches under the skimmer for solid covers, barely below normal for mesh. Stop there. The remaining water isn't laziness; it's ballast holding the shell in the ground.

6. Blow out the lines and plug returns

   Work line by line: push air until the return spits dry mist, plug it against the flowing air, move on. Skimmer, returns, cleaner line, in whatever order your plumbing prefers — dry pipes are the entire point of closing.

7. Protect the skimmer

   The skimmer throat is where trapped water has no escape — park a guard bottle or rated plug in it and let ice crush the cheap part.

8. Add pool antifreeze where blowouts fall short

   Any line you can't prove is dry gets pool-grade antifreeze at the label's rate per foot. Automotive antifreeze is toxic in this context — pool-rated only, always.

9. Drain the equipment

   Every vessel on the pad — pump, filter, heater, chlorinator — gets its drain plugs pulled. Drop all the plugs in the pump basket; that's the one place everyone looks first in spring.

10. Set the air pillow and cover

    Inflate the pillow to about two-thirds, center it, then bring the cover over and secure it per its design. Under ice, that soft dome is the difference between inward compression and outward wall pressure.

11. Store chemicals properly

    Seal opened containers, keep oxidizers and acids separated, and store everything cool, dry, and locked away from kids and pets — exactly as each label describes.

12. 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

The September crowd empties shelves in a predictable order. This is the short list worth owning before Aurora's window opens — nothing exotic, just the stuff everyone needs the same weekend.

• Cover pump

  Solid covers collect rain all winter; this is the drainage plan.

• Expansion plugs + skimmer guard

  Seals blown-out lines and sacrifices itself to skimmer ice.

• Pool antifreeze

  Pool-rated glycol for the lines air couldn't clear.

• Winter closing kit

  The under-the-cover chemistry, measured for your gallons.

• Air pillow

  Gives ice somewhere to push besides your pool walls.

• Winter cover

  The one purchase every other closing step depends on.

How Aurora compares locally

Two nearby data points to triangulate with: Denver, 9 miles from Aurora, models its close at October 1 (the same day); Centennial, 11 miles out, at September 30. Aurora's own window ends October 1. For the other half of the calendar see when to open in Aurora, or scan the full year on the season page.

The measuring stick here is Cherry Creek Dam — 8.1 miles to the southwest, elevation about 5647 feet. Its 1991–2020 record is what the model reads for Aurora; your backyard in Arapahoe 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 Aurora owners

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.

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.

Blowout first, antifreeze second

Air is the only guaranteed freeze protection: a line that's verifiably dry cannot burst. Antifreeze (pool-grade, per label) is the fallback for lines you can't confirm — long runs, low spots, water-feature plumbing. Doing antifreeze instead of a blowout, rather than in addition, is how most cracked returns happen.

Closing at 5647 feet

High-elevation autumns lie: Aurora 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.