More than 60 beaches were declared unsafe for swimming on Thursday following torrential rains and storm runoff on Tuesday and amid the ongoing dilution in the Merrimack River from last week's sewer overflow.
Plum Island beaches were still closed nearly two weeks after the Haverhill wastewater rupture, with dozens of other North Shore, Cape Cod and South Coast beaches added to the list after up to 6 inches or more of rain fell across the region on Monday and Tuesday.
Storm runoff typically affects beach water for 48 to 72 hours after a heavy rain event, with water test results lagging for up to two days after samples are taken for excessive bacteria.
The bacteria used as indicator organisms to test the waters at beaches are Enterococci and E. coli. Marine beaches are tested for the presence of Enterococci. Freshwater beaches are tested either for the presence of E. coli or Enterococci. Enteric bacteria are indicator organisms found in the intestines of warm-blooded animals and humans, often associated with fecal contamination.
An elevated presence of these organisms indicates the water may not be safe for human or animal consumption or contact, and may cause symptoms ranging from gastrointestinal pain to eye and ear discomfort to flu-like symptoms.
Most of these symptoms are minor, but occasionally a more serious illness may occur. Children, the elderly, and those with weakened immune systems are at greater risk of developing serious symptoms.
Some beach areas may remain open for recreational activities, though any contact with the water is strongly discouraged.
Massachusetts beaches closed as of 10 a.m. on Thursday included:
Latest Forecast (National Weather Service):
Thursday
Mostly sunny and hot, with a high near 91. Heat index values as high as 96. West wind 7 to 9 mph.
Thursday Night
Mostly cloudy, with a low around 71. Southwest wind 6 to 9 mph.
Friday
A chance of showers and thunderstorms after 2 p.m. Increasing clouds, with a high near 89. West wind 5 to 7 mph. Chance of precipitation is 40%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Friday Night
A chance of showers and thunderstorms before 8 p.m., then a slight chance of showers between 8 p.m. and 2 a.m. Mostly cloudy, with a low around 69. Light and variable wind. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Saturday
Mostly sunny, with a high near 83. North wind 5 to 8 mph becoming east in the afternoon.
Saturday Night
Partly cloudy, with a low around 66. Light and variable wind.
Sunday
Sunny, with a high near 82. North wind 5 to 9 mph becoming east in the afternoon.
Sunday Night
Mostly clear, with a low around 65. Light and variable wind.
Monday
Sunny, with a high near 85. Calm wind becoming south 5 to 9 mph in the afternoon.
Monday Night
Mostly clear, with a low around 68. Southwest wind 8 to 10 mph.
Tuesday
Mostly sunny and hot, with a high near 91. Southwest wind 8 to 14 mph.
Tuesday Night
Partly cloudy, with a low around 73. Southwest wind 9 to 11 mph.
Wednesday
Mostly sunny and hot, with a high near 93. West wind 9 to 13 mph.
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