Pool season · Pennsylvania
Bethlehem Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Bethlehem'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.
Bethlehem, PA — 92 swim days a yearThe bar compresses Bethlehem's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the April 22–May 13 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends October 9. Wherever the today marker sits, the nearest color change is your next appointment.
The Bethlehem pool calendar
Opening — target April 29
Open by April 29 — a two-week head start on the May 13 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 9
Hold the cover until September 29, then winterize by October 9, a week ahead of the October 24 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Bethlehem's typical-year water curve: the same EWMA model as the live widget, run on the 1991–2020 normals instead of this week's weather.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 32° | 30° | 37° | 47° | 58° | 67° | 74° | 75° | 70° | 60° | 49° | 39° |
The curve peaks near 76°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Allentown's pool season and Erie's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Pennsylvania season index.
Bethlehem pool season FAQ
When should I open my pool in Bethlehem, PA?
Open by April 29 — the model places Bethlehem's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Bethlehem opening guide has the 12-step sequence.
When should I close my pool in Bethlehem?
Close by October 9: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Bethlehem closing guide sequences the work backward from that date.
How long is the swim season in Bethlehem?
Bethlehem averages 92 days a year with normal highs of 80°F or better — right on the statewide median. The Pennsylvania season index ranks all 12 covered cities by the same metric.
How warm does pool water get in Bethlehem?
An unheated pool near Bethlehem typically peaks around 76°F in high summer and bottoms out near 30°F in winter, never quite reaching the 78°F comfort line without a heater or solar cover. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when Bethlehem hits the closing window
Data: NOAA 1991–2020 climate normals via Allentown International Airport (4.6 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.