Pool season · Illinois
Arlington Heights Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Arlington Heights 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.
Arlington Heights, IL — 75 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Arlington Heights's swim season; the hollow teal run before it (April 29 to May 20) is when to open; the hollow amber run after is when to close, with October 7 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Arlington Heights pool calendar
Opening — target May 6
Target May 6; the practical window runs April 29–May 20, and the 7-day mean crosses the 61°F threshold around May 20. Cold-water starts are the cheap ones.
Closing — deadline October 7
Hold the cover until September 27, then winterize by October 7, a week ahead of the October 26 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Arlington Heights'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 27° | 26° | 34° | 44° | 55° | 66° | 73° | 75° | 70° | 60° | 47° | 35° |
The curve peaks near 75°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Alton's pool season and Aurora's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Illinois season index.
Arlington Heights pool season FAQ
When should I open my pool in Arlington Heights, IL?
The site model recommends opening by May 6 — about two weeks before Arlington Heights'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 Arlington Heights opening guide.
When should I close my pool in Arlington Heights?
Winterize by October 7. The model holds the deadline a week ahead of Arlington Heights's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Arlington Heights closing guide.
How long is the swim season in Arlington Heights?
Arlington Heights averages 75 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 Arlington Heights?
An unheated pool near Arlington Heights typically peaks around 75°F in high summer and bottoms out near 25°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 Arlington Heights hits the closing window
Data: NOAA 1991–2020 climate normals via Chicago Palwaukee Airport (4.3 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.