Overnight Pool Temperature Drop Calculator
Predict how many degrees your pool will lose overnight. Calculate thermal loss based on air temperature, humidity, and cover status.
Thermal Thermodynamics
Water has a very high specific heat, but it is not infinite. A 10,000-gallon pool exposed to cool night air will radiate and evaporate its way through its thermal stores. Most of this loss occurs between **2:00 AM and 6:00 AM** when the air-to-water temperature delta is at its highest.
Pro Tip: If you are heating your pool for the next day, run your heater in the evening and put the cover on immediately. This "charges" the thermal mass of the pool.
Frequently Asked Questions
Can a fountain help cool a pool?
Yes! If your pool is too hot (above 92ะยฐF), running your aerator or fountain at night can drop the temperature by 3-5 degrees extra due to evaporative cooling. Use our Cooling Time Calculator for details.
Why is my pool losing more heat than usual?
Wind is likely the culprit. Even a light 10mph breeze can double your overnight heat loss if the pool is uncovered.
Get the Complete DIY Pool Maintenance Guide
Free PDF checklist including seasonal schedules, chemical balancing secrets, and maintenance tips.