Pool season · Illinois
Springfield Pool Season: the Year on One Bar
Last updated: July 25, 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.
Springfield, IL — 96 swim days a yearReading 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.
Every station tells its own story: compare this curve with Schaumburg's pool season and Waukegan's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Illinois season index.
Springfield pool season FAQ
When should I open my pool in Springfield, IL?
The site model recommends opening by April 26 — about two weeks before Springfield's 7-day mean temperature crosses 61°F, while the water is still too cold for algae. The step-by-step sequence is in the Springfield opening guide.
When should I close my pool in Springfield?
Winterize by October 11. The model holds the deadline a week ahead of Springfield's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Springfield closing guide.
How long is the swim season in Springfield?
Springfield averages 96 days a year with normal highs of 80°F or better — about 9 days earlier than the Illinois median. The Illinois season index ranks all 18 covered cities by the same metric.
How warm does pool water get in Springfield?
An unheated pool near Springfield typically peaks around 76°F in high summer and bottoms out near 27°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 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.