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Coldest sea in United States in September

4,477 coastal locations in United States ranked by typical September sea temperature, coldest first. Region-wide average in September: 21.5°C.

Coldest in September

Prudhoe Bay

2.6°C September mean in United States

Regional September average

21.5°C

across all 4,477 coastal locations in United States

Vs annual mean

+5.3°C

above the year-round regional average

What the United States sea feels like in September

Water at this temperature is very pleasant to swim in. If you tend to wear a wetsuit when swimming, you might consider removing it now to avoid the body overheating.

United States monthly average 10.0°C to 22.6°C
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  • Warmest month August 22.6°C
  • Coldest month February 10.0°C
  • Annual mean 16.2°C
  • Months above 20°C 3 of 12

Where September fits in the year

September sits inside the regional pattern shown on the left. Pick a different month to see how the ranking shifts.

All twelve United States month rankings:

United States sea temperature map (live)

The map shows today's latest reading at every United States location. The list below is based on the typical September mean.

Zoom in to see individual locations. Click a pin for water temperatures. View list →
°C -2 0 1 3 5 7 9 11 13 15 17 19 21 24 27 30 35

Top 50 coldest United States locations in September

Sorted by typical September mean from a decade of daily readings, coldest first. Click any place for the full location page.

# Location September mean
1 Prudhoe Bay Alaska 2.6°C
2 Flaxman Island Alaska 2.7°C
3 Cross Island (Dinkum Sands) Alaska 2.9°C
4 Barter Island Alaska 3.0°C
5 Prudhoe Bay #2 Alaska 3.0°C
6 Barrow Alaska 3.3°C
7 Barrow (offshore) Alaska 3.9°C
8 Point Barrow, Alaska Alaska 3.9°C
9 Point Barrow Alaska 3.9°C
10 Maknik Lagoon entrance, St. Lawrence Island, Alaska Alaska 7.0°C
11 Northeast Cape, St. Lawrence Island Alaska 7.0°C
12 Savoonga, St. Lawrence Island Alaska 7.0°C
13 Fossil River entrance, St. Lawrence Island, Alaska Alaska 7.1°C
14 Powooiliak Point, St. Lawrence Island, Alaska Alaska 7.2°C
15 Amukta Island, north side, Aleutian Islands, Alaska Alaska 7.3°C
16 Akeftapak, St. Lawrence Island Alaska 7.3°C
17 Moghoweyik River entrance, St. Lawrence Island, Alaska Alaska 7.4°C
18 St. Matthew Island, Bering Sea, Alaska Alaska 7.6°C
19 Point Hope Alaska 7.7°C
20 East Cove, Yunaska Island, Alaska Alaska 7.7°C
21 North side, Yunaska Island, Alaska Alaska 7.7°C
22 Applegate Cove, Chuginadak Island, Aleutian Islands, Alaska Alaska 7.7°C
23 Outside Lopp Lagoon Alaska 7.8°C
24 Ogliuga Island (east coast), Delarof Islands, Alaska Alaska 7.8°C
25 Fort Peck Lake Montana 7.9°C
Show 25 more ▸
26 Shishmaref Inlet 2 Alaska 8.0°C
27 Lash Bay, Tanaga Island, Alaska Alaska 8.0°C
28 Tin City, Bering Sea Alaska 8.0°C
29 Herbert Island, west side, Aleutian Islands, Alaska Alaska 8.1°C
30 Kivalina Alaska 8.1°C
31 Ulak Island, Delarof Islands, Alaska Alaska 8.1°C
32 Finch Cove, Seguam Island, Aleutian Islands, Alaska Alaska 8.1°C
33 Acadia Maine 8.2°C
34 Tanaga Bay, Tanaga Island, Alaska Alaska 8.2°C
35 Cape Espenberg, Kotzebue Sound Alaska 8.2°C
36 Gareloi Island, Delarof Islands, Alaska Alaska 8.3°C
37 Okee Bay, Umnak Island, Alaska Alaska 8.3°C
38 Inanudak Bay, Umnak Island, Alaska Alaska 8.3°C
39 Constantine Harbor, Amchitka Island, Rat Islands, Alaska Alaska 8.3°C
40 Constantine Harbour Alaska 8.3°C
41 South Bight, Amchitka Island, Rat Islands, Alaska Alaska 8.3°C
42 Cape Chunu, Kanaga Island, Alaska Alaska 8.4°C
43 Hot Springs Bay, Tanaga Island, Alaska Alaska 8.4°C
44 Otter Point, Umnak Island, Alaska Alaska 8.4°C
45 Red Dog Dock Alaska 8.4°C
46 Adugak Island, Aleutian Islands, Alaska Alaska 8.4°C
47 Adugak Islands, Umnak Island, Alaska Alaska 8.4°C
48 Cape Sagak, Umnak Island, Alaska Alaska 8.4°C
49 Lost River, Seward Peninsula Alaska 8.4°C
50 Skan Bay, Unalaska Island, Alaska Alaska 8.4°C

Warmest 10 in United States in September

Same data the other way. The warmest spots for the same month.

# Location September mean
1 Lake Pleasant Arizona 30.6°C
2 Lake Powell Arizona 30.6°C
3 Phoenix Arizona 30.6°C
4 Denver Colorado 30.5°C
5 Las Cruces New Mexico 30.4°C
6 Sawyer Key, inside, Cudjoe Channel, Florida Florida 30.3°C
7 Sawyer Key, outside, Cudjoe Channel, Florida Florida 30.3°C
8 Sawyer Key Florida 30.3°C
9 Fleming Key, north end Florida 30.3°C
10 Key West, south side, White Street Pier, Florida Florida 30.3°C

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