Pool season · Illinois
Naperville Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
Naperville'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.
Each dot on the bar is one week of Naperville's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (May 1–May 22), solid teal is swim season, and hollow amber is the closing window ending October 4. The black marker is today — its position against the colors is the entire executive summary.
The Naperville pool calendar
Opening — target May 8
Open by May 8 — a two-week head start on the May 22 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 4
Hold the cover until September 24, then winterize by October 4, a week ahead of the October 16 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Naperville'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 25° | 24° | 32° | 43° | 54° | 65° | 72° | 73° | 68° | 58° | 45° | 33° |
The curve peaks near 73°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Naperville hits the closing window
Data: NOAA 1991–2020 climate normals via Lisle-morton Arboretum (6.6 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.