Pool season · New Hampshire
Manchester Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Manchester'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.
Manchester, NH — 48 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Manchester's swim season; the hollow teal run before it (May 11 to June 1) is when to open; the hollow amber run after is when to close, with September 29 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Manchester pool calendar
Opening — target May 18
Target May 18; the practical window runs May 11–June 1, and the 7-day mean crosses the 61°F threshold around June 1. Cold-water starts are the cheap ones.
Closing — deadline September 29
Hold the cover until September 19, then winterize by September 29, a week ahead of the October 11 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Manchester'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 25° | 23° | 29° | 40° | 52° | 62° | 70° | 70° | 67° | 56° | 44° | 34° |
The curve peaks near 71°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Dover's pool season and Nashua's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the New Hampshire season index.
Manchester pool season FAQ
When should I open my pool in Manchester, NH?
The site model recommends opening by May 18 — about two weeks before Manchester'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 Manchester opening guide.
When should I close my pool in Manchester?
Winterize by September 29. The model holds the deadline a week ahead of Manchester's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Manchester closing guide.
How long is the swim season in Manchester?
Manchester averages 48 days a year with normal highs of 80°F or better — about 4 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 Manchester?
An unheated pool near Manchester typically peaks around 71°F in high summer and bottoms out near 22°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 Manchester hits the closing window
Data: NOAA 1991–2020 climate normals via Massabesic Lake (2.6 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.