Pool season · Pennsylvania
Philadelphia Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Philadelphia'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.
Philadelphia, PA — 109 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Philadelphia's swim season; the hollow teal run before it (April 8 to April 29) is when to open; the hollow amber run after is when to close, with October 22 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Philadelphia pool calendar
Opening — target April 15
Open by April 15 — a two-week head start on the April 29 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 22
The window opens October 12 once water leaves the algae zone; the model deadline is October 22, a week ahead of the November 17 freeze normal.
Estimated water temperature by month
This is Philadelphia'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 36° | 35° | 41° | 51° | 62° | 71° | 79° | 80° | 76° | 65° | 54° | 44° |
Warmest water typically July–August (peaking near 80°F); heaters and covers shift any month up.
Every station tells its own story: compare this curve with Lebanon's pool season and Pittsburgh's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Pennsylvania season index.
Philadelphia pool season FAQ
When should I open my pool in Philadelphia, PA?
The site model recommends opening by April 15 — about two weeks before Philadelphia's 7-day mean temperature crosses 61°F, while the water is still too cold for algae. The step-by-step sequence is in the Philadelphia opening guide.
When should I close my pool in Philadelphia?
Winterize by October 22. The model holds the deadline a week ahead of Philadelphia's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Philadelphia closing guide.
How long is the swim season in Philadelphia?
Philadelphia averages 109 days a year with normal highs of 80°F or better — about 14 days earlier than the Pennsylvania median. The Pennsylvania season index ranks all 12 covered cities by the same metric.
How warm does pool water get in Philadelphia?
An unheated pool near Philadelphia typically peaks around 80°F in high summer and bottoms out near 34°F in winter, spending roughly 2 months at or above the 78°F comfort line most swimmers prefer. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when Philadelphia hits the closing window
Data: NOAA 1991–2020 climate normals via Phila Franklin Inst (4.0 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.