Pool closing · Mississippi
When to Close Your Pool in Hattiesburg, MS: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Plan to close your Hattiesburg pool by November 13. The local 7-day mean temperature drops out of the algae-risk zone around November 3, and NOAA normals put the first 32°F freeze near November 23 — winterize between those dates and the water goes under the cover cold, clean, and easy to reopen. Below: today's water estimate, the full closing window, and a step-by-step winterizing checklist.
Hattiesburg closing dates at a glance
| Closing window | November 3 – November 13 |
|---|---|
| Close by (deadline) | November 13 |
| First freeze, 50% probability | November 23 |
| Open by (recommended) | March 9 |
| Opening window | March 2 – March 23 |
| 61°F crossing (7-day mean) | March 23 |
| Swim-season length (80°F+ days) | 170 days |
| NOAA normals station | Hattiesburg 5sw · 3.9 mi · 385 ft |
A classic four-season pool calendar: open early into cold water, close late into cold water, and Hattiesburg's 170 days of prime swimming sit safely in between.
Put dates aside and follow the water: the Hattiesburg curve says roughly 65°F by mid-April, 79°F by mid-June, 82°F in mid-August, then back down through 70°F in mid-October. The summer ceiling sits near 82°F, and every window above is just a line drawn on this curve.
The 12-step Hattiesburg 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.
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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.
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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
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
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
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
The skimmer throat is where trapped water has no escape — park a guard bottle or rated plug in it and let ice crush the cheap part.
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Add pool antifreeze where blowouts fall short
Antifreeze is the insurance policy for doubtful lines, not a replacement for the blowout: pool-grade product, label dosing, and only where air couldn't finish the job.
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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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Note this year's dates
Jot down when Hattiesburg's water actually cooled and when you closed. A two-line note beats memory next November 3 — your own yard runs a few days off any model, including ours.
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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
The November crowd empties shelves in a predictable order. This is the short list worth owning before Hattiesburg's window opens — nothing exotic, just the stuff everyone needs the same weekend.
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Pool antifreeze
Backup for unverifiable lines; label rate per foot of pipe.
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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
Sized to overlap; the cheapest insurance the pool wears all winter.
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Cover pump
Standing water is a cover killer; this is the counter.
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Expansion plugs + skimmer guard
Cheap rubber that stands between ice and your fittings.
How Hattiesburg compares locally
Two nearby data points to triangulate with: Gulfport, 63 miles from Hattiesburg, models its close at November 19 (about a week later); Slidell, 76 miles out, at November 19. Hattiesburg's own window ends November 13. For the other half of the calendar see when to open in Hattiesburg, or scan the full year on the season page.
Every number on this page traces to one instrument cluster: Hattiesburg 5sw, 3.9 miles south of Hattiesburg's center at an elevation near 385 feet. NOAA computed its 1991–2020 normals from roughly three decades of daily readings — long enough that one strange spring in Forrest County barely moves the dates.
Field notes for Hattiesburg owners
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.
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.
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.
Hattiesburg pool closing FAQ
What temperature should water be to close a pool?
Close once water holds below about 65°F — the point where algae go mostly dormant — and before hard freezes. In Hattiesburg, the 7-day mean drops through the threshold around November 3, so the window between then and November 13 is the sweet spot for a clean, stable close.
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. Hattiesburg's water doesn't settle below the risk zone until around November 3 — closing much before that trades a few weekends of maintenance for a rough spring.
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 Hattiesburg the freeze clock starts around November 23, so settle this during closing, not during the first cold snap.
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?
Two failure modes. Where freezes reach the plumbing, expansion cracks pumps, filters, and fittings from the inside. Where they don't, an unwatched pool simply drifts green and unbalanced by spring. Hattiesburg has no published freeze normal to pin the date, so the winterizing above plus forecast-watching covers both risks.
When is the last safe date to close in Hattiesburg?
The model draws the line at November 13 for Hattiesburg. It isn't arbitrary: the cool-down plus ten days (the freeze normal, November 23, leaves room to spare), and the whole closing sequence needs a working weekend of margin. The one exception that overrides any date — a hard freeze inside the 10-day forecast, which the widget above flags as urgent.
Email me when Hattiesburg hits the closing window
Data: NOAA 1991–2020 climate normals via Hattiesburg 5sw (3.9 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.