Pool season · Idaho
Nampa Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
This is the one-page view of Nampa'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.
Nampa, ID — 103 swim days a yearEach dot on the bar is one week of Nampa'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 2–May 23), solid teal is swim season, and hollow amber is the closing window ending October 3. The black marker is today — its position against the colors is the entire executive summary.
The Nampa pool calendar
Opening — target May 9
Open by May 9 — a two-week head start on the May 23 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 3
Hold the cover until September 23, then winterize by October 3, a week ahead of the October 13 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Nampa'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 30° | 34° | 41° | 48° | 55° | 64° | 72° | 76° | 69° | 58° | 45° | 35° |
The curve peaks near 77°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Meridian's pool season and Boise's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Idaho season index.
Nampa pool season FAQ
When should I open my pool in Nampa, ID?
Target May 9. That date backs off two weeks from the day Nampa's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the Nampa opening guide.
When should I close my pool in Nampa?
The closing deadline is October 3 — late enough that the water has cooled out of the algae zone, early enough to beat Nampa's first-freeze normal by about a week. See the Nampa closing guide for the winterizing steps.
How long is the swim season in Nampa?
Nampa averages 103 days a year with normal highs of 80°F or better — right on the statewide median. The Idaho season index ranks all 5 covered cities by the same metric.
How warm does pool water get in Nampa?
An unheated pool near Nampa typically peaks around 77°F in high summer and bottoms out near 30°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 Nampa hits the closing window
Data: NOAA 1991–2020 climate normals via Nampa Sugar Factory (1.5 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.