Pool closing · Washington
When to Close Your Pool in Redmond, WA: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Plan to close your Redmond 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 November 23 — 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.
Redmond closing dates at a glance
| Closing window | September 21 – October 1 |
|---|---|
| Close by (deadline) | October 1 |
| First freeze, 50% probability | November 23 |
| Open by (recommended) | May 31 |
| Opening window | May 24 – June 14 |
| 61°F crossing (7-day mean) | June 14 |
| Swim-season length (80°F+ days) | 0 days |
| NOAA normals station | Seattle Sand Pt WSFO · 6.5 mi · 60 ft |
A short season cuts both ways: every week opened before June 14 is a real slice of Redmond's roughly 0-day warm-swim budget.
The same model in water terms: Redmond's estimated pool temperature runs about 50°F in mid-April, 60°F in mid-June, 68°F in mid-August, and 56°F in mid-October, peaking near 68°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.
The 12-step Redmond winterizing checklist
A closing is a plumbing project with a chemistry warm-up. Start a few days ahead of your target date, keep every dose per its product label, and don't skip the photographs — spring-you reassembles from them.
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Balance the water a few days ahead
Three or four days before closing, adjust alkalinity and pH into label ranges. Balanced water is gentler on the liner, plaster, and equipment through the long covered months ahead.
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Deep-clean the pool
Leave nothing organic behind: skim the surface, brush every wall and step, vacuum the floor slowly. What goes under the cover dirty comes out worse — winter only ever compounds what it's given.
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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
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
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
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.
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Protect the skimmer
Install a skimmer guard bottle (or a plug rated for your skimmer) so ice that forms there crushes the sacrificial piece instead of cracking the skimmer body.
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Add pool antifreeze where blowouts fall short
Doubt is the criterion: any run you can't confirm dry gets pool-grade antifreeze at the label's per-foot rate. The automotive jug from the garage is for cars — it has no business in pool plumbing.
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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.
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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.
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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.
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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
A small stack of supplies turns the checklist above into a single-weekend job. Buy before Redmond's September rush and the whole list ships at leisure instead of sprinting.
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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
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
The one purchase every other closing step depends on.
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Cover pump
Solid covers collect rain all winter; this is the drainage plan.
How Redmond compares locally
Two nearby data points to triangulate with: Kirkland, 4 miles from Redmond, models its close at October 1 (the same day); Bellevue, 6 miles out, at October 1. Redmond's own window ends October 1. For the other half of the calendar see when to open in Redmond, or scan the full year on the season page.
Local means local: Redmond's dates come from Seattle Sand Pt WSFO, the nearest station with complete daily temperature normals — 6.5 miles west, about 60 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 Redmond owners
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.
Cold water is the whole point
A pool closed at 55°F barely changes all winter: algae are dormant, chemicals hold, and spring opens with a light dusting instead of a bloom. A pool closed at 72°F runs its own quiet ecosystem under the cover for a month. The date matters less than the water temperature it represents.
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.
Hard-winter homework
Where winter is long — Redmond banks only about 0 warm-swim days — the closing carries months of load. Bury the effort where it counts: verified-dry lines, fully drained equipment, a skimmer guard, and a cover secured for real wind. A short season forgives a late opening; it never forgives a cracked pump.
Redmond pool closing FAQ
What temperature should water be to close a pool?
Close once water holds below about 65°F — the point where algae go mostly dormant — and before hard freezes. In Redmond, the 7-day mean drops through the threshold around September 21, so the window between then and October 1 is the sweet spot for a clean, stable close.
Can you close a pool too early?
You can, and warm-water closings are why "we opened to a swamp" stories exist. The fix is patience: let Redmond's water cool through the mid-60s°F — around September 21 by our model — then close inside the window that ends October 1.
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 Redmond, so let the live forecast, not a calendar, tell you when freeze protection starts mattering.
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?
The repair list writes itself in order of cost: heater heat exchanger, pump housing, filter tank, then every fitting the ice reached — discovered one leak at a time in spring. Around Redmond the exposure begins near November 23, and each skipped checklist step above is one more candidate for that list.
When is the last safe date to close in Redmond?
October 1, by our model — the cool-down plus ten days (the freeze normal, November 23, leaves room to spare). Later closes happen, but they happen in gloves. The winterizing steps above take a weekend; leave yourself at least that much runway before Redmond's first freeze-risk stretch.
Email me when Redmond hits the closing window
Data: NOAA 1991–2020 climate normals via Seattle Sand Pt WSFO (6.5 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.