Pool season · Illinois
Bloomington Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Bloomington'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.
Bloomington, IL — 103 swim days a yearThe bar compresses Bloomington's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the April 23–May 14 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends October 8. Wherever the today marker sits, the nearest color change is your next appointment.
The Bloomington pool calendar
Opening — target April 30
Open by April 30 — a two-week head start on the May 14 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 8
The window opens September 28 once water leaves the algae zone; the model deadline is October 8, a week ahead of the October 16 freeze normal.
Estimated water temperature by month
This is Bloomington'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26° | 26° | 34° | 45° | 57° | 68° | 74° | 74° | 70° | 60° | 47° | 34° |
The curve peaks near 74°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Aurora's pool season and Champaign's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Illinois season index.
Bloomington pool season FAQ
When should I open my pool in Bloomington, IL?
Target April 30. That date backs off two weeks from the day Bloomington's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the Bloomington opening guide.
When should I close my pool in Bloomington?
The closing deadline is October 8 — late enough that the water has cooled out of the algae zone, early enough to beat Bloomington's first-freeze normal by about a week. See the Bloomington closing guide for the winterizing steps.
How long is the swim season in Bloomington?
Bloomington averages 103 days a year with normal highs of 80°F or better — about 5 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 Bloomington?
An unheated pool near Bloomington typically peaks around 74°F in high summer and bottoms out near 24°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 Bloomington hits the closing window
Data: NOAA 1991–2020 climate normals via Normal 4ne (5.2 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.