Pool closing · Washington
When to Close Your Pool in Kirkland, WA: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
In Kirkland, the closing window runs from September 21 to October 1. Let the water cool out of the algae-growth range before covering — close too warm and you lift the cover onto a green surprise in spring — but finish ahead of the first freeze, which normals place around November 23. The live estimate below shows where Kirkland's water sits today.
Kirkland 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 · 2.4 mi · 60 ft |
A short season cuts both ways: every week opened before June 14 is a real slice of Kirkland's roughly 0-day warm-swim budget.
Put dates aside and follow the water: the Kirkland curve says roughly 50°F by mid-April, 60°F by mid-June, 68°F in mid-August, then back down through 56°F in mid-October. The summer ceiling sits near 68°F, and every window above is just a line drawn on this curve.
The 12-step Kirkland winterizing checklist
Sequenced against Kirkland's September 21–October 1 window: chemistry while the pump still runs, blowouts before the equipment drains, cover last. Labels dictate every dose.
-
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.
-
Deep-clean the pool
Skim, brush walls and steps, and vacuum carefully. Any leaves or algae you seal under the cover become spring's chemistry problem, so closing day cleanliness pays twice.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
Cover pump
Keeps rain and melt off a solid cover all season.
-
Expansion plugs + skimmer guard
The blowout's finishing move — one per return, one for the skimmer.
-
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
Centers under the cover so ice pushes inward, not outward.
-
Winter cover
Measure with overlap; the winter workhorse over everything else.
How Kirkland compares locally
Two nearby data points to triangulate with: Redmond, 4 miles from Kirkland, models its close at October 1 (the same day); Bellevue, 7 miles out, at October 1. Kirkland's own window ends October 1. For the other half of the calendar see when to open in Kirkland, or scan the full year on the season page.
Local means local: Kirkland's dates come from Seattle Sand Pt WSFO, the nearest station with complete daily temperature normals — 2.4 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 Kirkland owners
The fifteen-minute monthly walk-around
Once a month all winter: pump or siphon standing water off solid covers, re-tension straps or top up water bags, confirm the level hasn't dropped enough to strand the cover, and glance at the pad for critter nests. Every major cover failure starts as a skipped walk-around.
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.
Hard-winter homework
Where winter is long — Kirkland 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.
Kirkland pool closing FAQ
What temperature should water be to close a pool?
Below roughly 65°F, and trending down. Water closed warm keeps feeding algae under the cover for weeks; water closed in the 50s goes dormant almost immediately. Kirkland's cool-down lands near September 21 in the normals, which is why the window opens there.
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 Kirkland, hold off until the cool-down near September 21 before covering.
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 Kirkland, 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 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 Kirkland 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 Kirkland?
Treat October 1 as the deadline in Kirkland. It's derived from the 1991–2020 normals: the cool-down plus ten days (the freeze normal, November 23, 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 Kirkland hits the closing window
Data: NOAA 1991–2020 climate normals via Seattle Sand Pt WSFO (2.4 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.