Pool season · Pennsylvania
Lancaster Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
Lancaster's whole pool calendar, condensed: when the water warms, when it cools, and where today falls between those edges. Use the opening guide and closing guide for the step-by-step work; keep this page for the dates.
The bar compresses Lancaster's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the April 20–May 11 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends October 10. Wherever the today marker sits, the nearest color change is your next appointment.
The Lancaster pool calendar
Opening — target April 27
Open by April 27 — a two-week head start on the May 11 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 10
The window opens September 30 once water leaves the algae zone; the model deadline is October 10, a week ahead of the October 24 freeze normal.
Estimated water temperature by month
Monthly averages of the site's water model run on Lancaster's own normals — the shape of a typical year, not a forecast. The widget above shows where the current year actually sits.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 33° | 31° | 37° | 48° | 58° | 67° | 75° | 75° | 71° | 61° | 49° | 40° |
The curve peaks near 76°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Lancaster hits the closing window
Data: NOAA 1991–2020 climate normals via Lancaster 2ne Fltr Plt (1.6 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.