When Should You
Close Your Pool?
Close too early and you'll open a green pool in spring. Close too late and a hard freeze can crack your plumbing. Here's the window for your state, worked out from 30 years of NOAA climate data, and the water-temperature rule that decides it.
The 65°F Rule (and Why 60°F Is Even Better)
The single most important closing rule has nothing to do with the calendar: close when your water temperature, measured mid-afternoon, holds below 65°F for a solid week. Two things happen below that line:
- Algae goes dormant. Growth slows dramatically in the low 60s and essentially stops near 50°F. Close warm and you've sealed a lit incubator under your cover.
- Your chemicals survive until spring. Chlorine is consumed two to three times faster in warm water. Close at 75°F and the winterizing dose is spent by December, leaving the pool unsanitized for months.
If you can comfortably wait until the water is near 60°F, do it. Below 50°F is the lowest-risk close of all. The industry shorthand is "close late, open early": the fewer warm, covered, unfiltered days your pool experiences, the cleaner it opens. Come spring, the same NOAA data gives you when to open your pool in your state.
Water Temperature, Not Air Temperature
Your pool is a flywheel: it banks a whole summer of heat and cools weeks behind the air. A 55°F cold snap in September doesn't make 55°F water; the pool may still be at 70°F. Track the water thermometer at mid-afternoon for 5 to 7 consecutive days before you commit.
When to Close Your Pool in Every State
Two dates for the main pool markets in every state. Close after the first, when the water has usually cooled below 65°F, and before the second, the median first freeze. The gap between them is your closing window.
Closing optional: January averages 47 to 53°F, mild enough to run the pool all winter with freeze protection on instead of closing.
Short window: 18 days or less between the two dates, so book early and close the week your water reaches 65°F.
Source: NOAA U.S. Climate Normals, 1991-2020. How these dates were worked out
| City | Close afterwater below 65°F | Close beforemedian first freeze |
|---|---|---|
| Alabama | All states | |
| BirminghamShort window | Oct 24 | Nov 11 |
| MobileClosing optional | Nov 4 | Nov 25 |
| Alaska | All states | |
| Anchorage | Any timewater rarely reaches 65°F | Oct 1 |
| Outdoor pools are rare here and almost always heated. Close well before the first freeze, which arrives around October 1 in Anchorage. | ||
| Arizona | All states | |
| Phoenix | Usually stays open all winterFreezes are rare (about 1 winter in 6) | |
| Tucson | Usually stays open all winterMedian first freeze Dec 9: keep freeze protection on | |
| Winter here means resting the pool, not closing it: shorter pump runs, freeze protection switched on, and the pump left running through the occasional freeze-warning night. | ||
| Arkansas | All states | |
| Little Rock | Oct 18 | Nov 10 |
| California | All states | |
| Los Angeles | Usually stays open all winterFreezes are rare | |
| SacramentoClosing optional | Oct 24 | Dec 2 |
| Most California pools never fully close; they drop to shorter winter pump hours with light chemistry. Mountain and high-desert pools follow a true freeze schedule and close in September or October. | ||
| Colorado | All states | |
| DenverShort window | Sep 23 | Oct 9 |
| Colorado Springs | Sep 19 | Oct 8 |
| Connecticut | All states | |
| Hartford | Sep 23 | Oct 16 |
| Bridgeport | Oct 1 | Nov 6 |
| Delaware | All states | |
| Wilmington | Oct 4 | Nov 1 |
| District of Columbia | All states | |
| Washington | Oct 13 | Nov 18 |
| Florida | All states | |
| Orlando | Usually stays open all winterMedian first freeze Jan 10: keep freeze protection on | |
| TallahasseeClosing optionalShort window | Nov 9 | Nov 21 |
| No closing needed in Central and South Florida. North Florida does freeze most winters (Tallahassee's median first freeze is in late November), so keep freeze protection on there and run the pump through freeze warnings. | ||
| Georgia | All states | |
| Atlanta | Oct 23 | Nov 20 |
| SavannahClosing optional | Nov 5 | Nov 30 |
| Hawaii | All states | |
| Honolulu | Usually stays open all winterFreezes are rare | |
| No closing needed. Check each fall that your equipment's freeze protection is switched on (many owners turn it off for summer), and run the pump through any freeze warning. | ||
| Idaho | All states | |
| Boise | Sep 27 | Oct 21 |
| Illinois | All states | |
| Chicago | Sep 27 | Oct 28 |
| SpringfieldShort window | Oct 2 | Oct 20 |
| Indiana | All states | |
| Indianapolis | Oct 1 | Oct 26 |
| Iowa | All states | |
| Des Moines | Sep 27 | Oct 20 |
| Kansas | All states | |
| Wichita | Oct 10 | Oct 29 |
| Kentucky | All states | |
| Louisville | Oct 12 | Nov 7 |
| Louisiana | All states | |
| New Orleans | Usually stays open all winterMedian first freeze Dec 31: keep freeze protection on | |
| ShreveportClosing optional | Oct 30 | Nov 18 |
| Maine | All states | |
| Portland | Sep 15 | Oct 15 |
| Maryland | All states | |
| Baltimore | Oct 5 | Oct 31 |
| Massachusetts | All states | |
| Boston | Sep 26 | Nov 9 |
| Worcester | Sep 16 | Oct 21 |
| Michigan | All states | |
| Detroit | Sep 24 | Oct 27 |
| Grand Rapids | Sep 20 | Oct 20 |
| Minnesota | All states | |
| Minneapolis | Sep 20 | Oct 18 |
| Mississippi | All states | |
| JacksonClosing optionalShort window | Oct 27 | Nov 14 |
| Missouri | All states | |
| St. Louis | Oct 9 | Nov 4 |
| Kansas City | Oct 3 | Oct 24 |
| Montana | All states | |
| Billings | Sep 15 | Oct 7 |
| Nebraska | All states | |
| Omaha | Sep 30 | Oct 21 |
| Nevada | All states | |
| Las VegasClosing optional | Nov 5 | Dec 15 |
| Reno | Sep 29 | Oct 23 |
| Two different climates. Las Vegas pools mostly stay open all winter, while Reno is a true freeze zone where pools close by mid-to-late October. | ||
| New Hampshire | All states | |
| ConcordShort window | Sep 15 | Oct 3 |
| New Jersey | All states | |
| Newark | Oct 5 | Nov 10 |
| Atlantic City | Oct 3 | Oct 29 |
| New Mexico | All states | |
| Albuquerque | Oct 8 | Nov 3 |
| New York | All states | |
| New York City | Oct 5 | Nov 20 |
| Albany | Sep 20 | Oct 15 |
| Upstate closes much earlier than the city: Albany's median first freeze is mid-October, about five weeks before New York City's. | ||
| North Carolina | All states | |
| CharlotteShort window | Oct 16 | Nov 3 |
| Wilmington | Oct 27 | Nov 20 |
| Two schedules: the Piedmont (Charlotte, Raleigh) closes in October, while the coast runs two to three weeks later. | ||
| North Dakota | All states | |
| FargoShort window | Sep 12 | Sep 30 |
| Ohio | All states | |
| Columbus | Sep 29 | Oct 27 |
| Cleveland | Sep 28 | Nov 3 |
| Oklahoma | All states | |
| Oklahoma City | Oct 14 | Nov 2 |
| Oregon | All states | |
| Portland | Sep 28 | Nov 19 |
| Pennsylvania | All states | |
| Philadelphia | Oct 7 | Nov 10 |
| Pittsburgh | Sep 24 | Oct 23 |
| Rhode Island | All states | |
| Providence | Sep 26 | Oct 30 |
| South Carolina | All states | |
| ColumbiaShort window | Oct 23 | Nov 7 |
| CharlestonClosing optional | Nov 2 | Nov 27 |
| South Dakota | All states | |
| Sioux FallsShort window | Sep 21 | Oct 6 |
| Tennessee | All states | |
| NashvilleShort window | Oct 16 | Nov 3 |
| Memphis | Oct 23 | Nov 16 |
| Texas | All states | |
| Dallas-Fort Worth | Oct 31 | Nov 24 |
| Houston | Usually stays open all winterMedian first freeze Dec 9: keep freeze protection on | |
| North Texas closes; the Gulf Coast and South Texas mostly stay open. If you stay open, keep a freeze plan: the February 2021 winter storm cracked plumbing on open pools across the state. | ||
| Utah | All states | |
| Salt Lake City | Sep 30 | Oct 31 |
| Vermont | All states | |
| Burlington | Sep 18 | Oct 15 |
| Virginia | All states | |
| Richmond | Oct 11 | Nov 4 |
| Norfolk | Oct 21 | Nov 23 |
| Washington | All states | |
| Seattle | Sep 19 | Nov 23 |
| Spokane | Sep 14 | Oct 12 |
| West Virginia | All states | |
| Charleston | Oct 3 | Oct 26 |
| Wisconsin | All states | |
| Milwaukee | Sep 24 | Oct 29 |
| Madison | Sep 16 | Oct 10 |
| Wyoming | All states | |
| Cheyenne | Sep 10 | Oct 1 |
How these dates were worked out: both come from NOAA's U.S. Climate Normals for 1991-2020, for each city's main weather station. The water date is when the normal daily average air temperature falls to 62°F; pools trail the air, so that is about when unheated water settles below 65°F. The freeze date is the median first night at 32°F, so in half of all years the first freeze comes earlier. That is a light freeze: the 28°F hard freezes that can crack plumbing come a median of 11 days later. Your own pool thermometer always beats a table.
Timing Details Most Guides Skip
Your cover type moves the dates
A mesh cover passes sunlight and fine debris, so mesh-covered pools green up faster: close later and open earlier. A solid cover blocks all light, buying you a wider margin on both ends. Figure the cover is worth a one-to-two-week shift either way.
Salt pools have a built-in closing bell
Salt chlorine generators switch off in cold water to protect the cell: Hayward's Aqua Rite below 50°F and Pentair's IntelliChlor at 52°F, give or take 3°F, according to their manuals. From then on the pool gets no new chlorine unless you add it, so if you haven't closed by the time your panel shows the cold-water cutoff, close that week: pull the cell, drain it fully, and store it indoors. A freeze-cracked cell is a $500+ part.
Don't wait for the leaves
Waiting until trees are bare means closing dangerously late up north. Close on water temperature and put a leaf net over the winter cover instead, then pull the net once the leaves finish, before the first snow.
The Indian-summer trap
Closed in early September and a late-September heat wave arrived? Warm water under a cover burns through winter chlorine in days and algae follows within 24 to 48 hours of it hitting zero. Pull back a corner of the cover, test, and re-dose. Better still, don't close until the forecast shows no rebound above 65°F.
Closing week is a good time to check your deck, too: pool deck care in your state, from the same NOAA climate data.
Hiring a Pro? Book in August.
Professional closings pile up between late September and mid-October, and the first cold week triggers a rush that stretches lead times to one or two weeks at exactly the moment you need them. Get on a schedule in August or early September; some companies discount September slots. And a fun fact: "National Pool Closing Day" (the third Saturday of September) is a retailer invention. By the 65°F rule it's too early for almost everyone south of Minneapolis.
Frequently Asked Questions
What water temperature should my pool be before closing?
Consistently below 65°F, measured mid-afternoon, and closer to 60°F is better. Algae goes dormant around 60°F, and cold water makes your winterizing chemicals last until spring instead of burning off by December. Below 50°F is the lowest-risk close of all.
Is it better to close a pool early or late?
Late. The rule of thumb is "close late, open early": every warm week your pool spends sealed under a cover consumes chlorine and feeds algae, while an open pool is still being filtered and sanitized. The only hard deadline is beating your first hard freeze.
What happens if I close my pool too early?
Warm water eats the winterizing chlorine within weeks, because chlorine is consumed two to three times faster than in cold water. Algae then grows unopposed under the cover all fall. That's why early-closed pools so often open green. Closing above 65°F water is the most common closing mistake there is.
Is it too late to close my pool in November?
Not if your plumbing hasn't been through a hard freeze yet. Across the South, November is the closing month. Up north it's a gamble: exposed pipes held below roughly 20°F for a few hours can crack. Winterize before the first hard freeze, not after it.
Do I go by air temperature or water temperature?
Water. A pool holds a whole summer's worth of heat and cools weeks behind the air, so a chilly September week can still leave the water at 70°F. Track the water thermometer at mid-afternoon for five to seven consecutive days before deciding.
Do I need to close my pool in Florida, Texas, or Arizona?
Usually no. You "winterize" by keeping it running. Verify your equipment's freeze-protection auto-run each fall (it engages around 37 to 38°F). Run the pump continuously through freeze warnings, because moving water rarely freezes, and never drain the pool. If a hard freeze arrives with power-outage risk, drain the pump, filter, and heater instead.
When should I close a saltwater pool?
Use the same 65°F rule as any other pool, and close no later than your salt cell's cold-water cutoff. Salt cells stop making chlorine in cold water: Hayward's Aqua Rite below 50°F and Pentair's IntelliChlor at 52°F, give or take 3°F, according to their manuals. Past that point the pool gets no new chlorine unless you add it. Remove the cell at both unions, drain it completely, and store it indoors so trapped water can't freeze and crack the plates.
How far ahead should I book a professional closing?
August or early September. Peak closing season is late September through mid-October, and one cold snap fills every crew's calendar for two weeks. If you'd rather have someone else handle it, find a verified pool pro near you.
Know Your Window? Now Close It Right.
The full step-by-step winterization guide covers chemistry, plumbing blow-out, covers, and every freeze-damage trap.
Related: When to Open Your Pool · Opening & Closing Checklist · Pool Salt Calculator