Pool season · Massachusetts
Cambridge Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
Cambridge'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.
Each dot on the bar is one week of Cambridge'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 Cambridge pool calendar
Opening — target May 10
Target May 10; the practical window runs May 3–May 24, and the 7-day mean crosses the 61°F threshold around May 24. Cold-water starts are the cheap ones.
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
This is Cambridge'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° | 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.
Email me when Cambridge hits the closing window
Data: NOAA 1991–2020 climate normals via Jamaica Plain (5.0 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.