Pool closing · Washington
When to Close Your Pool in Yakima, WA: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Circle October 6 on the Yakima 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 October 23. The window opens September 26 — the live widget below shows how this year is actually tracking against it.
Yakima closing dates at a glance
| Closing window | September 26 – October 6 |
|---|---|
| Close by (deadline) | October 6 |
| First freeze, 50% probability | October 23 |
| Open by (recommended) | May 3 |
| Opening window | April 26 – May 17 |
| 61°F crossing (7-day mean) | May 17 |
| Swim-season length (80°F+ days) | 90 days |
| NOAA normals station | Yakima #2 · 1.0 mi · 1142 ft |
Yakima banks only about 90 days of 80°F-plus afternoons — early opening weeks are the cheapest season extension available.
Four water checkpoints anchor Yakima's year in the model: mid-April at about 51°F, mid-June at 65°F, mid-August near the 74°F peak zone, and mid-October easing through 55°F. The dates in the table are where those numbers cross the thresholds that matter.
The 12-step Yakima 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.
-
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.
-
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
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.
-
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.
-
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
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.
-
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.
-
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.
-
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.
-
Stage the cover pump
Solid covers need drainage all winter: set a cover pump or siphon before the first storm, not after. Standing water strains seams and invites a mid-winter emergency.
-
Calendar the off-season checks
Set a monthly reminder from October 6 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 Yakima's September rush and the whole list ships at leisure instead of sprinting.
-
Cover pump
Solid covers collect rain all winter; this is the drainage plan.
-
Expansion plugs + skimmer guard
The blowout's finishing move — one per return, one for the skimmer.
-
Pool antifreeze
For lines you can't verify dry — pool-grade only, per label.
-
Winter closing kit
Season-length winter chemicals in one label-dosed box.
-
Air pillow
A soft target for the ice sheet, centered under the cover.
-
Winter cover
The one purchase every other closing step depends on.
How Yakima compares locally
Statewide context: across the 21 Washington cities we model, Yakima's October 6 deadline sits in the earliest quarter. Nearby, Wenatchee (59 mi) closes around October 7 and Kennewick (71 mi) around October 11 — treat gaps under a week as microclimate noise, not strategy. Spring planning restarts at the opening guide; the Yakima pool season page keeps the whole year in one view.
The measuring stick here is Yakima #2 — 1.0 miles to the southwest, elevation about 1142 feet. Its 1991–2020 record is what the model reads for Yakima; your backyard in Yakima 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 Yakima 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.
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.
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.
Hard-winter homework
Where winter is long — Yakima banks only about 90 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.
Yakima 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 Yakima's actual water; the normals say the durable cool-down arrives near September 26, and anything inside the window to October 6 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. Yakima's water doesn't settle below the risk zone until around September 26 — closing much before that trades a few weekends of maintenance for a rough spring.
Do I need antifreeze in pool lines?
It depends entirely on your confidence in the blowout. Lines that blew fully dry need nothing; anything uncertain — low runs, water features, a stubborn cleaner line — gets pool-grade antifreeze at the label's rate per foot. With Yakima's freeze clock starting near October 23, uncertainty is the thing to eliminate.
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?
Expect equipment damage first — cracked pump volutes, split filter tanks, ruptured heater exchangers — then plumbing leaks that surface at startup. In Yakima, normals put the first freeze near October 23; everything after that date is borrowed time for an unwinterized system.
When is the last safe date to close in Yakima?
Treat October 6 as the deadline in Yakima. It's derived from the 1991–2020 normals: the cool-down plus ten days (the freeze normal, October 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 Yakima hits the closing window
Data: NOAA 1991–2020 climate normals via Yakima #2 (1.0 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.