Pool season · Maine
Portland Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
This is the one-page view of Portland's pool year: both model windows, the estimated water-temperature curve, and today's live position on the season bar. The detailed checklists live on the opening and closing guides; this page is the calendar you check between them.
Portland, ME — 11 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Portland's swim season; the hollow teal run before it (May 16 to June 6) is when to open; the hollow amber run after is when to close, with September 27 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Portland pool calendar
Opening — target May 23
Open by May 23 — a two-week head start on the June 6 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 27
Hold the cover until September 17, then winterize by September 27, a week ahead of the October 15 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Portland'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26° | 24° | 30° | 40° | 50° | 60° | 68° | 70° | 66° | 56° | 45° | 35° |
The curve peaks near 71°F — comfortable-water months here usually involve a heater or a solar cover.
Portland pool season FAQ
When should I open my pool in Portland, ME?
Target May 23. That date backs off two weeks from the day Portland's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the Portland opening guide.
When should I close my pool in Portland?
The closing deadline is September 27 — late enough that the water has cooled out of the algae zone, early enough to beat Portland's first-freeze normal by about a week. See the Portland closing guide for the winterizing steps.
How long is the swim season in Portland?
Portland averages 11 days a year with normal highs of 80°F or better — right on the statewide median. The Maine season index ranks all 1 covered cities by the same metric.
How warm does pool water get in Portland?
An unheated pool near Portland typically peaks around 71°F in high summer and bottoms out near 24°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 Portland hits the closing window
Data: NOAA 1991–2020 climate normals via Portland International Jetport (2.4 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.