Pool season · Massachusetts
Somerville Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
Somerville'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.
The bar compresses Somerville's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the May 5–May 26 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends October 8. Wherever the today marker sits, the nearest color change is your next appointment.
The Somerville pool calendar
Opening — target May 12
Target May 12; the practical window runs May 5–May 26, and the 7-day mean crosses the 61°F threshold around May 26. Cold-water starts are the cheap ones.
Closing — deadline October 8
Hold the cover until September 28, then winterize by October 8, a week ahead of the November 9 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
Monthly averages of the site's water model run on Somerville'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 32° | 30° | 35° | 44° | 54° | 64° | 72° | 74° | 70° | 60° | 49° | 40° |
The curve peaks near 74°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Somerville hits the closing window
Data: NOAA 1991–2020 climate normals via Boston Logan International Airport (5.1 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.