Pool season · New Hampshire
Dover Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Dover'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.
Dover, NH — 41 swim days a yearReading it takes ten seconds: 52 dots, one per week. Solid teal is Dover's swim season; the hollow teal run before it (May 15 to June 5) is when to open; the hollow amber run after is when to close, with September 25 as the deadline; gray is the covered season. Today's marker shows where you stand in that cycle right now.
The Dover pool calendar
Opening — target May 22
Open by May 22 — a two-week head start on the June 5 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 25
Hold the cover until September 15, then winterize by September 25, a week ahead of the October 10 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Dover'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° | 24° | 30° | 40° | 51° | 60° | 68° | 70° | 65° | 55° | 44° | 34° |
The curve peaks near 70°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Portsmouth's pool season and Manchester's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the New Hampshire season index.
Dover pool season FAQ
When should I open my pool in Dover, NH?
Open by May 22 — the model places Dover's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Dover opening guide has the 12-step sequence.
When should I close my pool in Dover?
Close by September 25: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Dover closing guide sequences the work backward from that date.
How long is the swim season in Dover?
Dover averages 41 days a year with normal highs of 80°F or better — right on the statewide median. The New Hampshire season index ranks all 4 covered cities by the same metric.
How warm does pool water get in Dover?
An unheated pool near Dover typically peaks around 70°F in high summer and bottoms out near 23°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 Dover hits the closing window
Data: NOAA 1991–2020 climate normals via Durham 2 N (2.5 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.