The cleanest beaches around Boston Harbor? They're in Southie

The cleanest public beaches around Boston Harbor are Pleasure Bay and City Point in South Boston. That’s according to an annual report card from the nonprofit Save the Harbor/Save the Bay. The group grades 15 metropolitan beaches on how often they are safe for swimming during the summer.

Two other beaches in South Boston, along with Revere Beach and Nantasket beach in Hull also got high marks.

Revere Mayor Patrick Keefe called his town’s beach, “one of the cleanest urban beaches in the commonwealth.”

"The positive grade for Revere Beach and other beaches along this oceanfront really signifies what's been done in the commonwealth to protect the waters," Keefe told reporters gathered near the Revere shore for the report card's release.

Save the Harbor gave low grades to two beaches, advising people not to swim at King’s Beach in Lynn and Tenean Beach in Dorchester. The group's executive director, Chris Mancini, said both beaches suffer from outdated infrastructure, leading to contamination from cracked pipes, sewer and stormwater overflows and other sources.

In most of the other city beaches, swimmers should wait until 24 hours after heavy rain to avoid contamination from runoff and sewer overflows, he said.

"Except for South Boston, where you can swim every day, the 24-hour rule is a good common sense rule," Mancini said.

Intense, heavy downpours have become more common with climate change, and they are expected to increase further as the climate warms. The storms can trigger sewage combined with storm runoff to overflow into nearby rivers and bays. A recent study by Boston University researchers linked these sewer overflows to a higher risk for hospital visits.

Overall, the report card found a rainy 2023 led to a decline in average water quality, but most beaches remained safe for swimming most of the time.

The state Department of Public Health posts results online from tests of water quality at both ocean and freshwater beaches from mid-June through Labor Day and .

U.S. Representative Katherine Clark, whose district includes Revere, called for more funding to protect public beaches against the increasing threats of climate change.

"It takes serious investment," she said. "The kind that transformed Boston Harbor from one of the dirtiest in America into the jewel of New England."

Clarification: The state Department of Public Health posts beach water quality test results online. The state Department of Conservation and Recreation conducts the tests per health department regulations.