Pool closing · Washington
When to Close Your Pool in Auburn, WA: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Circle October 1 on the Auburn calendar. Closing earlier traps warm, algae-friendly water under the cover; closing later gambles the plumbing against the first freeze, which the 1991–2020 normals place near November 10. The window opens September 21 — the live widget below shows how this year is actually tracking against it.
Auburn closing dates at a glance
| Closing window | September 21 – October 1 |
|---|---|
| Close by (deadline) | October 1 |
| First freeze, 50% probability | November 10 |
| Open by (recommended) | May 21 |
| Opening window | May 14 – June 4 |
| 61°F crossing (7-day mean) | June 4 |
| Swim-season length (80°F+ days) | 0 days |
| NOAA normals station | Kent · 8.0 mi · 30 ft |
A short season cuts both ways: every week opened before June 4 is a real slice of Auburn's roughly 0-day warm-swim budget.
The same model in water terms: Auburn's estimated pool temperature runs about 51°F in mid-April, 62°F in mid-June, 68°F in mid-August, and 56°F in mid-October, peaking near 69°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.
The 12-step Auburn winterizing checklist
Sequenced against Auburn's September 21–October 1 window: chemistry while the pump still runs, blowouts before the equipment drains, cover last. Labels dictate every dose.
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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.
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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
Clean media goes into storage, dirty media comes out worse: backwash the sand or DE, rinse the cartridges, all per the manual, before anything drains.
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Apply winter chemicals per label
Winter chemicals go in before shutdown, not after: label-dosed, circulated for a few hours, distributed evenly. A floater dropped on still water protects one corner.
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Lower the water level
Check the cover manufacturer's spec before touching the hose: solid covers typically want water below the skimmer mouth, mesh often barely lower than normal. Full draining is off the table entirely.
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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
Give the skimmer something cheap to break: a guard bottle or rated plug absorbs the ice expansion that would otherwise split the housing.
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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.
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Drain the equipment
Open the drains on everything that holds water and let the pad empty completely. Cartridges and small equipment overwinter far better on a garage shelf than outside.
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Set the air pillow and cover
Center an inflated air pillow, then fit the cover and secure it with water bags, cable, or straps as designed. The pillow gives ice a place to push besides your walls.
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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.
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Calendar the off-season checks
Set a monthly reminder from October 1 to spring: check cover tension, pump off standing water, and glance at the water level. Fifteen minutes a month protects the whole closing job.
What to buy before the rush
Every item below sells out somewhere in Washington 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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Cover pump
Solid covers collect rain all winter; this is the drainage plan.
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Expansion plugs + skimmer guard
The blowout's finishing move — one per return, one for the skimmer.
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Pool antifreeze
Pool-rated glycol for the lines air couldn't clear.
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Winter closing kit
The under-the-cover chemistry, measured for your gallons.
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Air pillow
Gives ice somewhere to push besides your pool walls.
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Winter cover
Measure with overlap; the winter workhorse over everything else.
How Auburn compares locally
Auburn closes in the earliest quarter of Washington's calendar. Neighbors run close: Kent (6 mi away) models its deadline at October 1 (the same day vs Auburn's October 1), while Federal Way (6 mi) shows September 29. The spring mirror of this page is the Auburn opening guide, and the season overview draws both windows on a single bar.
Local means local: Auburn's dates come from Kent, the nearest station with complete daily temperature normals — 8.0 miles north, about 30 feet up. Between that station and a King County backyard there's always a degree or two of microclimate; the windows are built wide enough to carry it.
Field notes for Auburn owners
Match the drainage plan to the cover
Solid covers shed nothing — they need a cover pump staged before the first storm and checked after each one. Mesh covers drain themselves but pass silt that settles all winter. Either way, the plan is decided in October, not improvised in January when the cover is an ice sheet.
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.
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 for a real winter
A Auburn 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.
Auburn pool closing FAQ
What temperature should water be to close a pool?
The practical target is water in the low 60s°F or below at closing day. Our Auburn model has the sustained cool-down starting September 21; closing between then and October 1 means chemistry stays put and the spring reveal is a mild one.
Can you close a pool too early?
Yes — it's the most common closing mistake. Seal 70°F water under a cover and algae keep growing in the dark all autumn; the spring opening turns green and expensive. In Auburn, hold off until the cool-down near September 21 before covering.
Do I need antifreeze in pool lines?
Treat antifreeze as a backup, not a substitute: the real protection is air in dry lines. Where a full blowout isn't possible, pool-grade antifreeze per label is cheap insurance against a cracked pipe — worth it anywhere freezes are routine, and Auburn sees them from about November 10.
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?
Two failure modes. Where freezes reach the plumbing, expansion cracks pumps, filters, and fittings from the inside. Where they don't, an unwatched pool simply drifts green and unbalanced by spring. Auburn has no published freeze normal to pin the date, so the winterizing above plus forecast-watching covers both risks.
When is the last safe date to close in Auburn?
The model draws the line at October 1 for Auburn. It isn't arbitrary: the cool-down plus ten days (the freeze normal, November 10, leaves room to spare), and the whole closing sequence needs a working weekend of margin. The one exception that overrides any date — a hard freeze inside the 10-day forecast, which the widget above flags as urgent.
Email me when Auburn hits the closing window
Data: NOAA 1991–2020 climate normals via Kent (8.0 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.