Pool season · Illinois
Chicago Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
One bar, one year, one Chicago pool. The season bar below draws everything the model knows — opening window, prime season, closing window — against today's date, with the working details one click away on the opening and closing pages.
Reading it takes ten seconds: 52 dots, one per week. Solid teal is Chicago's swim season; the hollow teal run before it (May 5 to May 26) is when to open; the hollow amber run after is when to close, with October 9 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Chicago pool calendar
Opening — target May 12
Open by May 12 — a two-week head start on the May 26 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 November 5 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Chicago's own normals — the shape of a typical year, not a forecast. The widget above shows where the current year actually sits.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 27° | 27° | 34° | 43° | 53° | 64° | 72° | 74° | 71° | 60° | 48° | 36° |
The curve peaks near 74°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Chicago hits the closing window
Data: NOAA 1991–2020 climate normals via Chicago Northerly Island (4.2 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.