Pool closing · Alabama
When to Close Your Pool in Mobile, AL: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Target November 23 as the practical closing deadline in Mobile. Our model of NOAA 1991–2020 normals keeps the 7-day mean above 61°F until November 13; after that, cooling water winds algae down while you work the checklist below. The hard stop is equipment freeze damage — normals put Mobile's first 32°F night near December 6.
Mobile closing dates at a glance
| Closing window | November 13 – November 23 |
|---|---|
| Close by (deadline) | November 23 |
| First freeze, 50% probability | December 6 |
| Open by (recommended) | February 27 |
| Opening window | February 20 – March 13 |
| 61°F crossing (7-day mean) | March 13 |
| Swim-season length (80°F+ days) | 178 days |
| NOAA normals station | Mobile Dwtn Airport · 4.6 mi · 26 ft |
Mobile's 178-day warm season leaves comfortable margins on both ends — the windows above aim you at the cheap-chemistry versions of each transition.
Put dates aside and follow the water: the Mobile curve says roughly 67°F by mid-April, 81°F by mid-June, 84°F in mid-August, then back down through 74°F in mid-October. The summer ceiling sits near 84°F, and every window above is just a line drawn on this curve.
The 12-step Mobile winterizing checklist
The order matters more than the date: balanced water first, verified-dry lines before anything else freezes-proofs, and the cover only after everything below it is done. Work the list inside the window above.
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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
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
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.
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Lower the water level
Your cover's manual sets the number — commonly a few inches under the skimmer for solid covers, barely below normal for mesh. Stop there. The remaining water isn't laziness; it's ballast holding the shell in the ground.
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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
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
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
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
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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Remove and store ladders and rails
Pull ladders, rails, and the diving-board hardware; rinse, dry, and store them out of the weather. Anchor sockets get a dab of protectant so spring bolts turn freely.
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Winterize the water features
Waterfalls, slides, and spillover spas hold water in places gravity won't clear — blow those lines separately and plug them, or they'll be the one crack you find in spring.
What to buy before the rush
A small stack of supplies turns the checklist above into a single-weekend job. Buy before Mobile's November rush and the whole list ships at leisure instead of sprinting.
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Cover pump
Keeps rain and melt off a solid cover all season.
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Expansion plugs + skimmer guard
Cheap rubber that stands between ice and your fittings.
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Pool antifreeze
Pool-rated glycol for the lines air couldn't clear.
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Winter closing kit
The under-the-cover chemistry, measured for your gallons.
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Air pillow
Centers under the cover so ice pushes inward, not outward.
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Winter cover
Measure with overlap; the winter workhorse over everything else.
How Mobile compares locally
Statewide context: across the 10 Alabama cities we model, Mobile's November 23 deadline sits in the earliest quarter. Nearby, Pensacola (57 mi) closes around November 26 and Gulfport (59 mi) around November 19 — treat gaps under a week as microclimate noise, not strategy. Spring planning restarts at the opening guide; the Mobile pool season page keeps the whole year in one view.
Local means local: Mobile's dates come from Mobile Dwtn Airport, the nearest station with complete daily temperature normals — 4.6 miles southeast, about 26 feet up. Between that station and a Mobile County backyard there's always a degree or two of microclimate; the windows are built wide enough to carry it.
Field notes for Mobile 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.
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.
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.
Don't close a pool people are still using
With Mobile's long season, the question isn't "is it November?" but "has the water actually cooled?" The window running to November 23 exists because warm-water closings breed spring algae. If swimmers keep showing up through November, let them — patience here is free maintenance.
Mobile 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 Mobile model has the sustained cool-down starting November 13; closing between then and November 23 means chemistry stays put and the spring reveal is a mild one.
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 Mobile's water cool through the mid-60s°F — around November 13 by our model — then close inside the window that ends November 23.
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 Mobile's freeze clock starting near December 6, 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?
Expect equipment damage first — cracked pump volutes, split filter tanks, ruptured heater exchangers — then plumbing leaks that surface at startup. In Mobile, normals put the first freeze near December 6; everything after that date is borrowed time for an unwinterized system.
When is the last safe date to close in Mobile?
Treat November 23 as the deadline in Mobile. It's derived from the 1991–2020 normals: the cool-down plus ten days (the freeze normal, December 6, leaves room to spare). Weather varies year to year, so watch the 10-day forecast in late November — an early cold snap moves the real deadline, and the widget above flags exactly that.
Email me when Mobile hits the closing window
Data: NOAA 1991–2020 climate normals via Mobile Dwtn Airport (4.6 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.