The action comes following heavy rainfall.
Health officials say storm water runoff can have a negative impact by elevating bacterial levels and affecting bathing water quality.
The beaches closed are on the north shore:
Centre Island Sound
Laurel Hollow Beach
North Hempstead Beach Park
Piping Rock Beach Club
Sea Cliff Village Beach
In addition, Biltmore Beach Club in Massapequa is closed due to elevated bacterial levels.
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