Pool season · Minnesota
Plymouth Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Plymouth'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.
Plymouth, MN — 55 swim days a yearThe bar compresses Plymouth's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the May 3–May 24 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends September 28. Wherever the today marker sits, the nearest color change is your next appointment.
The Plymouth pool calendar
Opening — target May 10
Target May 10; the practical window runs May 3–May 24, and the 7-day mean crosses the 61°F threshold around May 24. Cold-water starts are the cheap ones.
Closing — deadline September 28
Hold the cover until September 18, then winterize by September 28, a week ahead of the October 12 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Plymouth'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 17° | 16° | 26° | 40° | 53° | 64° | 72° | 72° | 67° | 55° | 40° | 27° |
The curve peaks near 73°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Minneapolis's pool season and Rochester's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Minnesota season index.
Plymouth pool season FAQ
When should I open my pool in Plymouth, MN?
Open by May 10 — the model places Plymouth's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Plymouth opening guide has the 12-step sequence.
When should I close my pool in Plymouth?
Close by September 28: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Plymouth closing guide sequences the work backward from that date.
How long is the swim season in Plymouth?
Plymouth averages 55 days a year with normal highs of 80°F or better — right on the statewide median. The Minnesota season index ranks all 10 covered cities by the same metric.
How warm does pool water get in Plymouth?
An unheated pool near Plymouth typically peaks around 73°F in high summer and bottoms out near 15°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 Plymouth hits the closing window
Data: NOAA 1991–2020 climate normals via New Hope (4.1 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.