Pool season · Massachusetts
Leominster Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
Leominster'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 Leominster's whole pool year into one lane rope: gray floats for the off-season, hollow teal for the May 6–May 27 opening window, solid teal for swim weeks, hollow amber for the closing stretch that ends September 30. Wherever the today marker sits, the nearest color change is your next appointment.
The Leominster pool calendar
Opening — target May 13
Open by May 13 — a two-week head start on the May 27 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 30
The window opens September 20 once water leaves the algae zone; the model deadline is September 30, a week ahead of the October 11 freeze normal.
Estimated water temperature by month
Monthly averages of the site's water model run on Leominster'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 27° | 25° | 31° | 42° | 53° | 63° | 71° | 72° | 67° | 56° | 45° | 35° |
The curve peaks near 73°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Leominster hits the closing window
Data: NOAA 1991–2020 climate normals via Fitchburg Municipal Airport (2.3 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.