Intense rain over the past 24 hours has prompted Nassau to warn against swimming at six beaches as a precaution.
Runoff following heavy rainfall previously has raised bacteria levels above state standards for water quality, officials said on Wednesday.
At a seventh beach, Massapequa's Philip Healey Beach, bacteria levels have exceeded the limits, according to the county department of health. The county has closed it until further notice.
Storms can carry a host of contaminants into streams, rivers, lakes, ponds and bays, according to the U.S. Environmental Protection Agency, from fertilizers to leaked fuel.
Bacteria, it says, comes from several sources including: lawns, roads, leaky sanitary sewer lines, sanitary sewer cross-connections, animal waste and septic systems.
At the beaches other than Philip Healey, swimming can resume as of 7 a.m. on Thursday — "unless there is additional heavy rainfall or water samples reveal elevated bacterial levels," the county health officials said.
The three North Shore beaches swimmers should shun are:
North Hempstead Beach Park – Port Washington
Sea Cliff Village Beach – Sea Cliff
Tappen Beach – Glenwood Landing
And the three South Shore beaches where swimming also is ill-advised are:
Biltmore Beach Club – Massapequa
Hewlett Point Beach – East Rockaway
Island Park Beach – Island Park
For up-to-date recorded information on beach openings and closings, call 516-227-9700.