Pool season · Massachusetts
Leominster Pool Season: the Year on One Bar
Last updated: July 25, 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.
Leominster, MA — 68 swim days a yearThe 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.
Every station tells its own story: compare this curve with Lawrence's pool season and Lowell's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Massachusetts season index.
Leominster pool season FAQ
When should I open my pool in Leominster, MA?
The site model recommends opening by May 13 — about two weeks before Leominster's 7-day mean temperature crosses 61°F, while the water is still too cold for algae. The step-by-step sequence is in the Leominster opening guide.
When should I close my pool in Leominster?
Winterize by September 30. The model holds the deadline a week ahead of Leominster's NOAA 50% first-freeze date, so the plumbing is protected before the first hard night. The full sequence is in the Leominster closing guide.
How long is the swim season in Leominster?
Leominster averages 68 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 Leominster?
An unheated pool near Leominster typically peaks around 73°F in high summer and bottoms out near 24°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 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.