Applies to: In-ground and above-ground pools in hot or mild climates that stay open all year; chlorine and salt-chlorine systems; pools with or without a heater. Check your own equipment manual for anything specific to your filter, pump, heater or chlorinator.
Quick answer
CDC lists sunlight among the things that reduce chlorine and recommends testing chlorine and pH at least twice a day. In a pool that never closes, that routine runs all year. Before a hurricane, UF/IFAS Extension advises against draining the pool. When you hear thunder, go indoors.[1][2][3]
How sun and heat change your water
CDC lists sunlight among the things that reduce chlorine, along with sweat and dirt from swimmers. It recommends testing chlorine and pH at least twice a day, more often when many people swim.[1]
CDC recommends a pH of 7.0 to 7.8 and at least 1 ppm chlorine in pools. If you use cyanuric acid, which CDC calls a chlorine stabilizer, or chlorine products that contain it (often sold as dichlor or trichlor), CDC recommends at least 2 ppm chlorine. CDC also notes that disinfection takes longer when cyanuric acid is present.[1]
CDC says chlorine works less well as pH rises, especially above 8.0. Follow your test kit maker's directions.[1]
EPA WaterSense names evaporation as a leading cause of pool water loss, especially in hot, drier climates, and notes warmer water evaporates faster.[4]
Algae and debris pressure
In a pool that never closes, upkeep cannot take a season off. UF/IFAS Extension notes that untreated or undertreated water will result in algae growth.[5]
If water turns green, Bestway's FAQ for its above-ground pools says to restore the chemical balance with help from a local pool chemical dealer.[6]
- EPA WaterSense suggests choosing landscape plants that won't add more debris to the pool. Shade from landscaping can also keep the water cooler and reduce evaporation.[4]
- UF/IFAS Extension advises against pressure-washing into the pool, and notes there are no chemical treatments to remove fertilizers from pool water.[2]
Store chemicals for the heat
Read the product label before every use, and dose only as the label directs for your pool's volume.[9]
Before a hurricane or severe storm
These steps come from UF/IFAS Extension in Florida. Follow local emergency officials first.
- Keep the water in. UF/IFAS Extension says not to drain or partially drain the pool before a storm. Water pressing on a drained pool could crack it, and a pool drained below the skimmer could burn up the pump motor. Keep it full until the storm passes and the ground drains.[2]
- Keep furniture out of the pool. UF/IFAS warns never to put outdoor furniture in the pool, because water and chemicals corrode it and can permanently stain the pool finish.[2]
- Shock only by the label. UF/IFAS notes you may shock the pool before the storm arrives. Follow the product label exactly.[2][9]
- Know your pump guidance. UF/IFAS suggests keeping the pump running while the power is still on. Bestway advises not using its filter pumps during a storm when thunder or lightning is present. Follow your own manual. Do not go out to tend the pool during the storm: the National Weather Service says there is no safe place outside when thunderstorms are in the area.[2][6][11]
- For above-ground pools, Bestway's FAQ warns that overfilling could make its pools collapse, and notes that after heavy rainfall you may need to empty some water to get the level right. Follow your own pool's manual.[12]
After the storm
- Check for hazards first. UF/IFAS says not to start any cleanup until the area is safe, with no downed power lines, and to watch for unexpected wildlife.[2]
- Remove debris before it breaks down and stains the pool finish.[2]
- Lower the level only when the ground has dried. UF/IFAS says to bring the water level back down once standing water around the pool has cleared, and never to turn your back on a draining pool.[2]
- Check your chemical levels again once cleanup is finished.[2]
Winter swimming in a mild climate
Hayward's heater manual says that in moderate climates its heaters can keep running through short cold spells, but it says not to use the heater for freeze protection or to hold the water just above freezing. Check your own heater manual.[10]
- EPA WaterSense says pool covers both reduce evaporation and help the water hold heat.[13]
- If you will be away for several days, EPA WaterSense suggests turning the heater off or the temperature down.[4]
When to call a professional
Common questions
- Should I drain my pool before a hurricane?
- No, according to UF/IFAS Extension. It advises keeping the pool full until after the storm, and notes a partially drained pool could crack under the weight of water outside it.[2]
- Why does my chlorine drop so fast in summer?
- CDC lists sunlight, sweat and dirt from swimmers among the things that reduce chlorine. It recommends testing chlorine and pH at least twice a day.[1]
- Can I put patio furniture in the pool so it doesn't blow away?
- UF/IFAS Extension says never. Water and chemicals corrode furniture and can permanently stain the pool finish.[2]
- Can my heater protect the pool from a freeze?
- Hayward's heater manual says not to use its heaters for freeze protection. Check your own heater's manual.[10]
Sources
Official sources, checked October 13, 2026. Manufacturer instructions apply to the product named; follow the manual and label for your own equipment and products.
- CDC: Home Pool and Hot Tub Water Treatment and Testing (May 10, 2024) (cdc.gov)
- UF/IFAS Extension Indian River County: Pools and Hurricanes (blogs.ifas.ufl.edu)
- NOAA National Weather Service: Lightning Safety Tips (weather.gov)
- EPA WaterSense: Jump Into Pool Water Efficiency (EPA-832-F-22-015, Sept 2022) (epa.gov)
- UF/IFAS EDIS: Closing Your Seasonal Home (HE887) (edis.ifas.ufl.edu)
- Bestway USA: Pool Maintenance FAQs (bestwayusa.com)
- CDC: Pool Chemical Safety (Aquatics Professionals Toolkit) (cdc.gov)
- CDC: Store Chemicals Safely (poster) (cdc.gov)
- CDC: Use Chemicals Safely (poster) (cdc.gov)
- Hayward: Pool and Spa/Hot Tub Heaters H150FD-H500FD Service & Installation Manual (hayward.com)
- NOAA National Weather Service: Lightning Safety (weather.gov)
- Bestway USA: Pool Assembly FAQs (bestwayusa.com)
- EPA WaterSense: Pool Water Efficiency (epa.gov)
- CPSC Pool Safely: Safety Tips (poolsafely.gov)
- Southern Nevada Water Authority: Track Down Leaks (snwa.com)
- HRSA, U.S. Department of Health & Human Services: Poison Help (home) (poisonhelp.hrsa.gov)
Related pool care guides
Water safety for your family
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