Pool season · New Hampshire
Nashua Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
One bar, one year, one Nashua 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.
Nashua, NH — 76 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Nashua's swim season; the hollow teal run before it (May 6 to May 27) is when to open; the hollow amber run after is when to close, with October 1 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Nashua pool calendar
Opening — target May 13
Open by May 13 — a two-week head start on the May 27 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 1
Hold the cover until September 22, then winterize by October 1, a week ahead of the October 8 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Nashua'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26° | 25° | 31° | 41° | 53° | 63° | 72° | 72° | 68° | 57° | 45° | 34° |
The curve peaks near 73°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Manchester's pool season and Portsmouth's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the New Hampshire season index.
Nashua pool season FAQ
When should I open my pool in Nashua, NH?
Target May 13. That date backs off two weeks from the day Nashua's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the Nashua opening guide.
When should I close my pool in Nashua?
The closing deadline is October 1 — late enough that the water has cooled out of the algae zone, early enough to beat Nashua's first-freeze normal by about a week. See the Nashua closing guide for the winterizing steps.
How long is the swim season in Nashua?
Nashua averages 76 days a year with normal highs of 80°F or better — about 9 days earlier than the New Hampshire median. The New Hampshire season index ranks all 4 covered cities by the same metric.
How warm does pool water get in Nashua?
An unheated pool near Nashua typically peaks around 73°F in high summer and bottoms out near 24°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 Nashua hits the closing window
Data: NOAA 1991–2020 climate normals via Nashua Cwsu (1.1 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.