Season geography
Across Kansas's featured cities, typical openings spread from May 10 to May 15, closings from Sep 24 to Oct 1, and the unheated season runs 132–144 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.