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Is it too cold to swim in Nantucket today?
The latest reading is 57°F (13.9°C), measured November 5, 2026 at 9:30 AM EST at Nantucket Island. That is very cold water.
Between 50°F and 60°F, rated very dangerous to immediately life-threatening: the range where most unacclimated people have a maximum cold shock response. Temperature is only one factor: check rip current and surf alerts, and swim near lifeguards.
How cold is too cold to swim?Water temperature this week
Hourly water temperature at Nantucket Island
Water temperature through the year
Average water temperature by month, satellite 2016–2025. Warmest in August.
Average ocean temperature by month
| Month | Average | Coldest year | Warmest year |
|---|---|---|---|
| January | 41°F | 37°F | 43°F |
| February | 39°F | 37°F | 40°F |
| March | 40°F | 38°F | 42°F |
| April | 45°F | 43°F | 47°F |
| May | 52°F | 50°F | 54°F |
| June | 61°F | 59°F | 63°F |
| July | 69°F | 67°F | 71°F |
| August | 71°F | 69°F | 73°F |
| September | 68°F | 65°F | 70°F |
| October | 61°F | 60°F | 64°F |
| November | 53°F | 51°F | 55°F |
| December | 45°F | 42°F | 47°F |
Other water temperature readings nearby
| Source | Water | Distance | Updated |
|---|---|---|---|
| NASA JPL MUR satellite nearest water | 55°F | 0.3 mi | Nov 3 |
| NANTUCKET SOUND buoy | 57°F | 17 mi | 2 h ago |
Water temperatures at nearby beaches
Frequently asked questions
Is it too cold to swim in Nantucket today?
The latest reading is 57°F (13.9°C), measured November 5, 2026 at 9:30 AM EST at Nantucket Island. That is very cold water. Between 50°F and 60°F, rated very dangerous to immediately life-threatening: the range where most unacclimated people have a maximum cold shock response. Temperature is only one factor: check rip current and surf alerts, and swim near lifeguards. How cold is too cold?
When is the water warmest at Nantucket?
Based on satellite data from 2016 to 2025, the water is warmest in August (average 71°F) and coldest in February (average 39°F).
Where does this water temperature come from?
From Nantucket Island, a tide station operated by NOAA National Data Buoy Center, 1.0 mi away. See the methodology.
Sources: NOAA National Data Buoy Center; NASA JPL MUR satellite analysis; forecast and alerts from the National Weather Service. Readings are provisional. All Massachusetts water temperatures · Methodology