Pool season · Massachusetts
Lynn Pool Season: the Year on One Bar
Last updated: July 15, 2026 · dates · water temp
This is the one-page view of Lynn's pool year: both model windows, the estimated water-temperature curve, and today's live position on the season bar. The detailed checklists live on the opening and closing guides; this page is the calendar you check between them.
Each dot on the bar is one week of Lynn'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 16–June 6), solid teal is swim season, and hollow amber is the closing window ending September 30. The black marker is today — its position against the colors is the entire executive summary.
The Lynn pool calendar
Opening — target May 23
Open by May 23 — a two-week head start on the June 6 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 30
Hold the cover until September 20, then winterize by September 30, a week ahead of the October 20 freeze normal. Late and cold beats early and warm.
Estimated water temperature by month
This is Lynn'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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 29° | 27° | 32° | 41° | 51° | 60° | 69° | 70° | 66° | 57° | 46° | 37° |
The curve peaks near 71°F — comfortable-water months here usually involve a heater or a solar cover.
Email me when Lynn hits the closing window
Data: NOAA 1991–2020 climate normals via Marblehead (5.4 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.