Pool season · Illinois
Joliet Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Joliet 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.
Joliet, IL — 81 swim days a yearThe bar compresses Joliet's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the April 28–May 19 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends October 7. Wherever the today marker sits, the nearest color change is your next appointment.
The Joliet pool calendar
Opening — target May 5
Open by May 5 — a two-week head start on the May 19 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 7
The window opens September 27 once water leaves the algae zone; the model deadline is October 7, a week ahead of the October 25 freeze normal.
Estimated water temperature by month
Monthly averages of the site's water model run on Joliet'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26° | 25° | 33° | 44° | 55° | 66° | 73° | 73° | 70° | 60° | 46° | 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 Evanston's pool season and Naperville's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Illinois season index.
Joliet pool season FAQ
When should I open my pool in Joliet, IL?
The site model recommends opening by May 5 — about two weeks before Joliet'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 Joliet opening guide.
When should I close my pool in Joliet?
Winterize by October 7. The model holds the deadline a week ahead of Joliet's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Joliet closing guide.
How long is the swim season in Joliet?
Joliet averages 81 days a year with normal highs of 80°F or better — right on the statewide median. The Illinois season index ranks all 18 covered cities by the same metric.
How warm does pool water get in Joliet?
An unheated pool near Joliet 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 Joliet hits the closing window
Data: NOAA 1991–2020 climate normals via Joliet Brandon Rd Dam (2.6 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.