Pool season · Massachusetts
Lynn Pool Season: the Year on One Bar
Last updated: July 25, 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.
Lynn, MA — 30 swim days a yearEach 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.
Every station tells its own story: compare this curve with Lowell's pool season and New Bedford's — neighboring normals stations can shift the windows by a week or more. The full ranking lives on the Massachusetts season index.
Lynn pool season FAQ
When should I open my pool in Lynn, MA?
Target May 23. That date backs off two weeks from the day Lynn's 7-day mean temperature reaches 61°F, so you start up in cold, algae-resistant water. Work the full checklist in the Lynn opening guide.
When should I close my pool in Lynn?
The closing deadline is September 30 — late enough that the water has cooled out of the algae zone, early enough to beat Lynn's first-freeze normal by about a week. See the Lynn closing guide for the winterizing steps.
How long is the swim season in Lynn?
Lynn averages 30 days a year with normal highs of 80°F or better — about 10 days later than the Massachusetts median. The Massachusetts season index ranks all 14 covered cities by the same metric.
How warm does pool water get in Lynn?
An unheated pool near Lynn typically peaks around 71°F in high summer and bottoms out near 26°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 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.