| Caspar Headlands State Beach | California | Coastal Waters | 13.1°C(55.6°F) | August, September, October, November | Live SST → |
| Castle Rock Beach | California | Gulf of California | 20.2°C(68.4°F) | July, August, September, October | Live SST → |
| Caswell Beach | North Carolina | Gulf of Mexico | 27°C(80.6°F) | June, July, August, September | Live SST → |
| Cayucos State Beach | California | Gulf of California | 15.4°C(59.7°F) | August, September, October, November | Live SST → |
| Cedar Beach | New York | James Bay | 21.2°C(70.2°F) | June, July, August, September | Live SST → |
| Cedar Grove Beach | New York | James Bay | 21.8°C(71.2°F) | June, July, August, September | Live SST → |
| Cedar Island | Massachusetts | James Bay | 20.2°C(68.4°F) | June, July, August, September | Live SST → |
| Cedar Island Beach | United States | Coastal Waters | 24.8°C(76.6°F) | July, August, September | Live SST → |
| Cedar Overlook Beach | New York | James Bay | 21.5°C(70.7°F) | June, July, August, September | Live SST → |
| Central Beach | California | Gulf of California | 20.8°C(69.4°F) | July, August, September, October | Live SST → |
| Chadwick Beach | New Jersey | Coastal Waters | 22.3°C(72.1°F) | July, August, September | Live SST → |
| Chalker Beach | Connecticut | James Bay | 20.9°C(69.6°F) | July, August, September, October | Live SST → |
| Chapman Beach | Connecticut | James Bay | 20.9°C(69.6°F) | July, August, September, October | Live SST → |
| Charles E. Ransom Beach | New York | James Bay | 21.7°C(71.1°F) | June, July, August, September | Live SST → |
| Chicken Ranch Beach | California | Coastal Waters | 13.2°C(55.8°F) | August, September, October, November | Live SST → |
| Children's Pool Beach | California | Gulf of California | 21.2°C(70.2°F) | July, August, September, October | Live SST → |
| Childrens Beach | Massachusetts | Coastal Waters | 19.1°C(66.4°F) | July, August, September, October | Live SST → |
| China Cove Beach | California | Gulf of California | 20.8°C(69.4°F) | July, August, September, October | Live SST → |
| China Ladder Beach | California | Gulf of California | 14.9°C(58.8°F) | July, August, September, October | Live SST → |
| Chito Beach | Washington | Coastal Waters | 11.6°C(52.9°F) | June, July, August, September | Live SST → |
| Chocomount Beach | New York | James Bay | 19.7°C(67.5°F) | July, August, September, October | Live SST → |
| Christi Beach | California | Gulf of California | 18.2°C(64.8°F) | July, August, September, October | Live SST → |
| Christian Camp Meeting Beach | Massachusetts | James Bay | 19.6°C(67.3°F) | June, July, August, September | Live SST → |
| Chuns Reef Beach | Hawaii | Coastal Waters | 26.8°C(80.2°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Circle Beach | Connecticut | James Bay | 21.6°C(70.9°F) | July, August, September, October | Live SST → |
| Clam Beach | California | Coastal Waters | 12.6°C(54.7°F) | September, October, November, December | Live SST → |
| Clean Shore | Massachusetts | Coastal Waters | 19.1°C(66.4°F) | July, August, September, October | Live SST → |
| Clearwater Beach | Florida | Gulf of Mexico | 29.5°C(85.1°F) | May, Jun, Jul, Aug, Sep, Oct | Live SST → |
| Cliff Beach | Massachusetts | Coastal Waters | 19.1°C(66.4°F) | July, August, September, October | Live SST → |
| Cliff House Beach | Maine | James Bay | 16.1°C(61°F) | June, July, August, September | Live SST → |
| Cliffwood Beach | New Jersey | James Bay | 21.9°C(71.4°F) | June, July, August, September | Live SST → |
| Clinton Beach | Connecticut | James Bay | 20.9°C(69.6°F) | July, August, September, October | Live SST → |
| Clinton Town Beach | Connecticut | James Bay | 21.6°C(70.9°F) | July, August, September, October | Live SST → |
| Coast Guard Beach | Massachusetts | James Bay | 18.3°C(64.9°F) | June, July, August, September | Live SST → |
| Coast Royale Beach | California | Gulf of California | 20.8°C(69.4°F) | July, August, September, October | Live SST → |
| Cobble Beach | Maine | James Bay | 13.5°C(56.3°F) | July, August, September, October | Live SST → |
| Cocoloba Beach | United States | Caribbean Sea | 29.2°C(84.6°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Coki Point Beach | United States | Caribbean Sea | 29.2°C(84.6°F) | January, February, March, April, May, June, July, August, September, October, November, December | Live SST → |
| Cold Spring Beach | New York | James Bay | 21.5°C(70.7°F) | June, July, August, September | Live SST → |
| College Cove North | California | Coastal Waters | 12.8°C(55°F) | July, August, September, November | Live SST → |
| College Cove South | California | Coastal Waters | 12.8°C(55°F) | July, August, September, November | Live SST → |
| Collins Beach | United States | James Bay | 19.6°C(67.3°F) | July, August, September, October | Live SST → |
| Collins Cove Beach | Massachusetts | James Bay | 17.5°C(63.5°F) | June, July, August, September | Live SST → |
| Columbia Beach | Oregon | Coastal Waters | 14.7°C(58.5°F) | June, July, August, September | Live SST → |
| Compass Rose Beach | Rhode Island | James Bay | 19.6°C(67.3°F) | July, August, September, October | Live SST → |
| Compo Beach | Connecticut | James Bay | 22.3°C(72.1°F) | July, August, September | Live SST → |
| Coney Island Beach | New York | James Bay | 21.8°C(71.2°F) | June, July, August, September | Live SST → |
| Conochet Club Beach | Rhode Island | James Bay | 19.6°C(67.3°F) | July, August, September, October | Live SST → |
| Cooks Beach | New Jersey | Coastal Waters | 23°C(73.4°F) | July, August, September | Live SST → |
| Cooks Brook Beach | Massachusetts | James Bay | 18.6°C(65.5°F) | June, July, August, September | Live SST → |