| Keawakapu Beach North | Hawaii | Coastal Waters | 26.8°C(80.2°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Keawakapu Beach South | Hawaii | Coastal Waters | 26.8°C(80.2°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Keawanui Beach | Hawaii | North Pacific Ocean | 27.3°C(81.1°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Kehena Beach | Hawaii | Coastal Waters | 26.6°C(79.9°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Kehoe Beach | California | Coastal Waters | 13.2°C(55.8°F) | August, September, October, November | Live SST → |
| Keʻe Beach | Hawaii | North Pacific Ocean | 27.1°C(80.8°F) | January, February, April, May, June, July, August, September, October, November, December | Live SST → |
| Kelham Beach | California | Coastal Waters | 14.2°C(57.6°F) | July, August, September, October | Live SST → |
| Keller Beach | California | Coastal Waters | 14.5°C(58.1°F) | July, August, September, October | Live SST → |
| Kenilworth Beach | Illinois | James Bay | 20.1°C(68.2°F) | July, August, September, October | Live SST → |
| Kenneys Road Beach | New York | James Bay | 20.9°C(69.6°F) | July, August, September, October | Live SST → |
| Keonenui Beach | Hawaii | Coastal Waters | 26.9°C(80.4°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Kepuhi Beach | Hawaii | Coastal Waters | 26.9°C(80.4°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Key West | Florida | Straits of Florida / Gulf of Mexico | 30.1°C(86.2°F) | Apr, May, Jun, Jul, Aug, Sep, Oct, Nov | Live SST → |
| Keyes Beach | Massachusetts | James Bay | 19.6°C(67.3°F) | June, July, August, September | Live SST → |
| Keystone Spit | Washington | Coastal Waters | 11.4°C(52.5°F) | June, July, August, September | Live SST → |
| Kiahuna Beach | Hawaii | North Pacific Ocean | 27°C(80.6°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Kiawah Beachwalker Park | South Carolina | Gulf of Mexico | 27.5°C(81.5°F) | June, July, August, September | Live SST → |
| Kiddie Beach | California | Gulf of California | 19.4°C(66.9°F) | July, August, September, October | Live SST → |
| Kiddie's Beach | Connecticut | James Bay | 20.4°C(68.7°F) | July, August, September, October | Live SST → |
| Kiʻekiʻe Beach | Hawaii | North Pacific Ocean | 27.3°C(81.1°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Kimbles Beach | New Jersey | Coastal Waters | 23°C(73.4°F) | July, August, September | Live SST → |
| King Park Beach | Rhode Island | James Bay | 19.6°C(67.3°F) | July, August, September, October | Live SST → |
| Kings Beach | Massachusetts | James Bay | 17.6°C(63.7°F) | June, July, August, September | Live SST → |
| Kingsborough Beach Park | New York | James Bay | 21.8°C(71.2°F) | June, July, August, September | Live SST → |
| Kiwanda Beach | Oregon | Coastal Waters | 13.9°C(57°F) | June, July, August, September | Live SST → |
| Kiwanda Beach | Oregon | Coastal Waters | 13.9°C(57°F) | June, July, August, September | Live SST → |
| Kiwanis Beach | Michigan | James Bay | 16.6°C(61.9°F) | July, August, September, October | Live SST → |
| Klondike Beach | Florida | Gulf of Mexico | 28.3°C(82.9°F) | May, June, July, August, September, October | Live SST → |
| Knollwood Beach | New York | James Bay | 21.5°C(70.7°F) | June, July, August, September | Live SST → |
| Ko Olina | Hawaii | Coastal Waters | 27°C(80.6°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Kōkī Beach | Hawaii | Coastal Waters | 26.7°C(80.1°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Kuhn Spit | Washington | Coastal Waters | 11.4°C(52.5°F) | June, July, August, September | Live SST → |
| L Street Bathing Beach | New Jersey | Coastal Waters | 21.9°C(71.4°F) | June, July, August, September | Live SST → |
| L Street Beach | Massachusetts | James Bay | 17.6°C(63.7°F) | June, July, August, September | Live SST → |
| La Conchita Beach | California | Gulf of California | 18.8°C(65.8°F) | July, August, September, October | Live SST → |
| La Costa Beach | California | Gulf of California | 20.2°C(68.4°F) | July, August, September, October | Live SST → |
| La Jolla Beach | California | Gulf of California | 19.4°C(66.9°F) | July, August, September, October | Live SST → |
| La Jolla Cove | California | Gulf of California | 21.2°C(70.2°F) | July, August, September, October | Live SST → |
| La Jolla Shores Beach | California | Gulf of California | 21.2°C(70.2°F) | July, August, September, October | Live SST → |
| La Piedra Beach | California | Gulf of California | 19.4°C(66.9°F) | July, August, September, October | Live SST → |
| Lagoon Beach | Hawaii | Coastal Waters | 27.1°C(80.8°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Laite Memorial Beach | Maine | James Bay | 14.1°C(57.4°F) | July, August, September, October | Live SST → |
| Lake Anza Beach | California | Coastal Waters | 14.5°C(58.1°F) | July, August, September, October | Live SST → |
| Lake Michigan Beach | Michigan | James Bay | 18.1°C(64.6°F) | July, August, September, October | Live SST → |
| Lake Mohegan Beach | Connecticut | James Bay | 22.3°C(72.1°F) | July, August, September | Live SST → |
| Lake Street Beach | Massachusetts | James Bay | 17.8°C(64°F) | June, July, August, September | Live SST → |
| Lakeside Beach | Michigan | James Bay | 19.3°C(66.7°F) | July, August, September, October | Live SST → |
| Lamberts Cove Beach | Massachusetts | James Bay | 20°C(68°F) | July, August, September, October | Live SST → |
| Lamoine Beach | Maine | James Bay | 12.8°C(55°F) | July, August, September, October | Live SST → |
| Langdon Beach | Illinois | James Bay | 20.1°C(68.2°F) | July, August, September, October | Live SST → |