Pool season · Illinois
Springfield Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
One bar, one year, one Springfield 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 Springfield's swim season; the hollow teal run before it (April 19 to May 10) is when to open; the hollow amber run after is when to close, with October 11 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Springfield pool calendar
Opening — target April 26
Open by April 26 — a two-week head start on the May 10 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 11
The window opens October 1 once water leaves the algae zone; the model deadline is October 11, a week ahead of the October 22 freeze normal.
Estimated water temperature by month
This is Springfield'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 29° | 28° | 37° | 48° | 59° | 69° | 75° | 75° | 71° | 61° | 48° | 37° |
The curve peaks near 76°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Springfield hits the closing window
Data: NOAA 1991–2020 climate normals via Springfield #2 (2.2 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.