Pool season · Illinois
Rockford Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
This is the one-page view of Rockford's pool year: both model windows, the estimated water-temperature curve, and today's live position on the season bar. The detailed checklists live on the opening and closing guides; this page is the calendar you check between them.
Rockford, IL — 81 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Rockford's swim season; the hollow teal run before it (April 27 to May 18) is when to open; the hollow amber run after is when to close, with October 4 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Rockford pool calendar
Opening — target May 4
Target May 4; the practical window runs April 27–May 18, and the 7-day mean crosses the 61°F threshold around May 18. Cold-water starts are the cheap ones.
Closing — deadline October 4
Hold the cover until September 24, then winterize by October 4, a week ahead of the October 17 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Rockford'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 24° | 23° | 32° | 44° | 55° | 66° | 73° | 73° | 69° | 58° | 45° | 32° |
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 Peoria's pool season and Round Lake Beach's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Illinois season index.
Rockford pool season FAQ
When should I open my pool in Rockford, IL?
Open by May 4 — the model places Rockford's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Rockford opening guide has the 12-step sequence.
When should I close my pool in Rockford?
Close by October 4: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Rockford closing guide sequences the work backward from that date.
How long is the swim season in Rockford?
Rockford 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 Rockford?
An unheated pool near Rockford typically peaks around 74°F in high summer and bottoms out near 22°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 Rockford hits the closing window
Data: NOAA 1991–2020 climate normals via Rockford Gtr Rockford Airport (4.8 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.