Pool closing · Virginia
When to Close Your Pool in Arlington, VA: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Target October 25 as the practical closing deadline in Arlington. Our model of NOAA 1991–2020 normals keeps the 7-day mean above 61°F until October 15; after that, cooling water winds algae down while you work the checklist below. The hard stop is equipment freeze damage — normals put Arlington's first 32°F night near November 18.
Arlington closing dates at a glance
| Closing window | October 15 – October 25 |
|---|---|
| Close by (deadline) | October 25 |
| First freeze, 50% probability | November 18 |
| Open by (recommended) | April 10 |
| Opening window | April 3 – April 24 |
| 61°F crossing (7-day mean) | April 24 |
| Swim-season length (80°F+ days) | 112 days |
| NOAA normals station | Washington Reagan Airport · 4.2 mi · 10 ft |
Arlington's 112-day warm season leaves comfortable margins on both ends — the windows above aim you at the cheap-chemistry versions of each transition.
The same model in water terms: Arlington's estimated pool temperature runs about 56°F in mid-April, 75°F in mid-June, 80°F in mid-August, and 64°F in mid-October, peaking near 81°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.
The 12-step Arlington winterizing checklist
Sequenced against Arlington's October 15–October 25 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
Do the chemistry midweek, close on the weekend: alkalinity and pH into label ranges with days of circulation left to spread them. Winter locks in whatever state the water holds on closing day.
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Deep-clean the pool
Brush, skim, and vacuum like company's coming. A pool that goes under the cover spotless comes out needing a rinse; one that goes under dirty comes out needing a project.
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Service the filter one last time
Backwash sand or DE, or pull and rinse cartridges, per the manual. A filter stored dirty cakes over winter and starts spring half-clogged.
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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.
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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
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
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.
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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
Open every drain plug on the pump, filter, heater, and chlorinator, and store the plugs in the pump basket so spring reassembly is a one-stop hunt. Move what you can indoors.
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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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Calendar the off-season checks
Set a monthly reminder from October 25 to spring: check cover tension, pump off standing water, and glance at the water level. Fifteen minutes a month protects the whole closing job.
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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.
What to buy before the rush
A small stack of supplies turns the checklist above into a single-weekend job. Buy before Arlington's October rush and the whole list ships at leisure instead of sprinting.
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Winter cover
Measure with overlap; the winter workhorse over everything else.
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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
Seals blown-out lines and sacrifices itself to skimmer ice.
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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
Season-length winter chemicals in one label-dosed box.
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Air pillow
Gives ice somewhere to push besides your pool walls.
How Arlington compares locally
Arlington closes in the earlier half of Virginia's calendar. Neighbors run close: Alexandria (4 mi away) models its deadline at October 25 (the same day vs Arlington's October 25), while Washington (5 mi) shows October 21. The spring mirror of this page is the Arlington opening guide, and the season overview draws both windows on a single bar.
Local means local: Arlington's dates come from Washington Reagan Airport, the nearest station with complete daily temperature normals — 4.2 miles southeast, about 10 feet up. Between that station and a Arlington County backyard there's always a degree or two of microclimate; the windows are built wide enough to carry it.
Field notes for Arlington owners
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.
The warm spell after you closed
A 78°F week in October doesn't mean reopening. Water under an opaque cover warms far less than air suggests, and a closed, balanced pool tolerates a warm stretch fine. Check the cover pump has somewhere to send rain, enjoy the weather, and leave the plumbing sealed.
Gas heaters get the manual, not a guess
Every heater brand sequences its winterizing differently — drain plugs, blower considerations, gas supply, control settings. The generic advice (drain fully, close the valve) is right but incomplete; ten minutes with your model's manual protects the most expensive component you'll winterize.
Arlington 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. Arlington's cool-down lands near October 15 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 Arlington, hold off until the cool-down near October 15 before covering.
Do I need antifreeze in pool lines?
Blown-out, plugged lines don't need it; doubtful lines do. Use only antifreeze labeled for pools, at the label's rate per foot of pipe — never automotive antifreeze. In Arlington the freeze clock starts around November 18, so settle this during closing, not during the first cold snap.
How far should I drain my pool for winter?
Only to the line your cover manufacturer prints — a few inches below the skimmer for most solid covers, close to operating level for many mesh designs with the skimmer plugged. The water you leave in is structural: it holds the shell against groundwater all winter.
What happens if you don't winterize a pool?
In a freeze climate, physics wins: water expands about 9% when it freezes, cracking pump housings, filter tanks, heat exchangers, and pipes. With Arlington's first 32°F night arriving near November 18 in the normals, an unwinterized pad is a spring repair bill waiting to be discovered.
When is the last safe date to close in Arlington?
October 25, by our model — the cool-down plus ten days (the freeze normal, November 18, 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 Arlington's first freeze-risk stretch.
Email me when Arlington hits the closing window
Data: NOAA 1991–2020 climate normals via Washington Reagan Airport (4.2 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.