Pool season · Iowa
Waterloo Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Waterloo 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.
Waterloo, IA — 92 swim days a yearThe bar compresses Waterloo's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the April 24–May 15 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends October 3. Wherever the today marker sits, the nearest color change is your next appointment.
The Waterloo pool calendar
Opening — target May 1
Target May 1; the practical window runs April 24–May 15, and the 7-day mean crosses the 61°F threshold around May 15. Cold-water starts are the cheap ones.
Closing — deadline October 3
The window opens September 25 once water leaves the algae zone; the model deadline is October 3, a week ahead of the October 10 freeze normal.
Estimated water temperature by month
Monthly averages of the site's water model run on Waterloo'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 21° | 21° | 31° | 44° | 56° | 68° | 74° | 74° | 69° | 58° | 44° | 31° |
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 Sioux City's pool season and Cedar Rapids's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Iowa season index.
Waterloo pool season FAQ
When should I open my pool in Waterloo, IA?
The site model recommends opening by May 1 — about two weeks before Waterloo'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 Waterloo opening guide.
When should I close my pool in Waterloo?
Winterize by October 3. The model holds the deadline a week ahead of Waterloo's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Waterloo closing guide.
How long is the swim season in Waterloo?
Waterloo averages 92 days a year with normal highs of 80°F or better — right on the statewide median. The Iowa season index ranks all 6 covered cities by the same metric.
How warm does pool water get in Waterloo?
An unheated pool near Waterloo typically peaks around 74°F in high summer and bottoms out near 19°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 Waterloo hits the closing window
Data: NOAA 1991–2020 climate normals via Waterloo Municipal Airport (5.0 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.