Season geography
Across Alabama's featured cities, typical openings spread from Mar 31 to Apr 23, closings from Oct 12 to Nov 3, and the unheated season runs 173–217 days depending on where you are. 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.