Pool season · Massachusetts
Boston Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
Boston'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.
Boston, MA — 76 swim days a yearEach dot on the bar is one week of Boston'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 3–May 24), solid teal is swim season, and hollow amber is the closing window ending October 6. The black marker is today — its position against the colors is the entire executive summary.
The Boston pool calendar
Opening — target May 10
Open by May 10 — a two-week head start on the May 24 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline October 6
Hold the cover until September 26, then winterize by October 6, a week ahead of the October 23 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Boston'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 30° | 29° | 34° | 43° | 54° | 64° | 73° | 74° | 70° | 59° | 48° | 38° |
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 Worcester's pool season and Brockton's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Massachusetts season index.
Boston pool season FAQ
When should I open my pool in Boston, MA?
Open by May 10 — the model places Boston's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Boston opening guide has the 12-step sequence.
When should I close my pool in Boston?
Close by October 6: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Boston closing guide sequences the work backward from that date.
How long is the swim season in Boston?
Boston averages 76 days a year with normal highs of 80°F or better — right on the statewide median. The Massachusetts season index ranks all 14 covered cities by the same metric.
How warm does pool water get in Boston?
An unheated pool near Boston typically peaks around 74°F in high summer and bottoms out near 28°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 Boston hits the closing window
Data: NOAA 1991–2020 climate normals via Jamaica Plain (2.3 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.