Pool closing · Texas
When to Close Your Pool in Houston, TX: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Two dates decide a Houston closing: November 20, when the 7-day mean drops back through 61°F and the water goes algae-quiet, and November 30, the model deadline set a safe week ahead of the December 25 first-freeze normal. Everything on this page — live water estimate, window, winterizing sequence — exists to land you between them.
Houston closing dates at a glance
| Closing window | November 20 – November 30 |
|---|---|
| Close by (deadline) | November 30 |
| First freeze, 50% probability | December 25 |
| Open by (recommended) | February 18 |
| Opening window | February 11 – March 4 |
| 61°F crossing (7-day mean) | March 4 |
| Swim-season length (80°F+ days) | 186 days |
| NOAA normals station | Houston-port · 7.1 mi · 19 ft |
Closing is close to optional here — many Houston owners trade the cover for shorter pump hours and swim the shoulder seasons. If you do close, the late window above still applies.
Four water checkpoints anchor Houston's year in the model: mid-April at about 69°F, mid-June at 82°F, mid-August near the 86°F peak zone, and mid-October easing through 75°F. The dates in the table are where those numbers cross the thresholds that matter.
The 12-step Houston winterizing checklist
Sequenced against Houston's November 20–November 30 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
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.
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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.
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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
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.
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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
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.
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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
Pillow first, cover second, tension last. A properly centered pillow turns the winter ice sheet from a wall-pressing ram into a harmless dome.
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Note this year's dates
Jot down when Houston's water actually cooled and when you closed. A two-line note beats memory next November 20 — your own yard runs a few days off any model, including ours.
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Shut down the heater carefully
Follow the manufacturer's winterizing sequence for your heater — drain it fully and, for gas units, close the supply valve. Heat exchangers are the most expensive freeze casualty on the pad.
What to buy before the rush
The November crowd empties shelves in a predictable order. This is the short list worth owning before Houston's window opens — nothing exotic, just the stuff everyone needs the same weekend.
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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
Backup for unverifiable lines; label rate per foot of pipe.
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Winter closing kit
Closing chemistry in one box, dosed by pool volume.
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Air pillow
A soft target for the ice sheet, centered under the cover.
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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 Houston compares locally
Two nearby data points to triangulate with: Pearland, 16 miles from Houston, models its close at December 4 (about a week later); Pasadena, 17 miles out, at December 3. Houston's own window ends November 30. For the other half of the calendar see when to open in Houston, or scan the full year on the season page.
The measuring stick here is Houston-port — 7.1 miles to the southeast, elevation about 19 feet. Its 1991–2020 record is what the model reads for Houston; your backyard in Harris 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 Houston owners
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.
The skimmer is the most breakable part you own
Skimmer bodies crack because water freezes inside the throat with nowhere to push. A sacrificial bottle or spring-loaded guard absorbs that expansion for a few dollars. It's the highest-return item in the entire closing kit relative to what it protects.
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.
Don't close a pool people are still using
With Houston's long season, the question isn't "is it November?" but "has the water actually cooled?" The window running to November 30 exists because warm-water closings breed spring algae. If swimmers keep showing up through November, let them — patience here is free maintenance.
Houston 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 Houston model has the sustained cool-down starting November 20; closing between then and November 30 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 Houston, hold off until the cool-down near November 20 before covering.
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 Houston's freeze clock starting near December 25, uncertainty is the thing to eliminate.
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?
In a freeze climate, physics wins: water expands about 9% when it freezes, cracking pump housings, filter tanks, heat exchangers, and pipes. With Houston's first 32°F night arriving near December 25 in the normals, an unwinterized pad is a spring repair bill waiting to be discovered.
When is the last safe date to close in Houston?
Our model's practical deadline is November 30 — set by the cool-down plus ten days (the freeze normal, December 25, leaves room to spare). Push much past it and you're winterizing in freeze-warning weather, rushing the blowout, and hoping the cover goes on before the first hard night. Inside the November 20–November 30 window, none of that drama applies.
Email me when Houston hits the closing window
Data: NOAA 1991–2020 climate normals via Houston-port (7.1 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.