Pool season · Michigan
South Lyon Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
This is the one-page view of South Lyon'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.
South Lyon, MI — 44 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is South Lyon's swim season; the hollow teal run before it (May 8 to May 29) is when to open; the hollow amber run after is when to close, with September 28 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The South Lyon pool calendar
Opening — target May 15
Target May 15; the practical window runs May 8–May 29, and the 7-day mean crosses the 61°F threshold around May 29. Cold-water starts are the cheap ones.
Closing — deadline September 28
The window opens September 18 once water leaves the algae zone; the model deadline is September 28, a week ahead of the October 13 freeze normal.
Estimated water temperature by month
This is South Lyon'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 25° | 22° | 29° | 40° | 52° | 62° | 69° | 70° | 66° | 56° | 44° | 33° |
The curve peaks near 70°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Saginaw's pool season and Southfield's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Michigan season index.
South Lyon pool season FAQ
When should I open my pool in South Lyon, MI?
Target May 15. That date backs off two weeks from the day South Lyon's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the South Lyon opening guide.
When should I close my pool in South Lyon?
The closing deadline is September 28 — late enough that the water has cooled out of the algae zone, early enough to beat South Lyon's first-freeze normal by about a week. See the South Lyon closing guide for the winterizing steps.
How long is the swim season in South Lyon?
South Lyon averages 44 days a year with normal highs of 80°F or better — about 5 days later than the Michigan median. The Michigan season index ranks all 23 covered cities by the same metric.
How warm does pool water get in South Lyon?
An unheated pool near South Lyon typically peaks around 70°F in high summer and bottoms out near 22°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 South Lyon hits the closing window
Data: NOAA 1991–2020 climate normals via Whitmore Lake 1nw (6.9 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.