Season geography
Across Florida's featured cities, typical openings spread from Feb 16 to Mar 17, closings from Nov 14 to Dec 15, and the unheated season runs 242–365 days depending on where you are. Miami stays warm enough to skip closing entirely. Elevation, coastal water, and urban heat all pull real dates around, which is exactly why a state-level answer isn't enough.
For your exact town, the pool season lookup takes a ZIP code. Opening day itself is a chemistry job — the dosing calculator turns your first test reading of the year into exact amounts.