Record-setting, smelly Sargassum seaweed headed for South Florida in May
The total amount of sargassum in the eastern Caribbean and western Atlantic set a new record in April and exceeded the previous all-time high in June 2022. Researchers say the exact reason for this record-setting amount of seaweed still needs to be investigated, but some of this seaweed belt will arrive on South Florida shores this month.
Will smelly sargassum seaweed make a comeback along Florida beaches?
We’re well into the summer season and people continue to flock to beaches to catch some rays and take a dip in the ocean. One thing people aren’t missing, however, is the smelly sargassum seaweed that has littered beaches across the U.S., including Florida, which saw a record-breaking invasion of the sargassum last year. FOX Weather Correspondent Brandy Campbell was in Fort Lauderdale on Wednesday and spoke to some beachgoers about their concerns.
MIAMI – Florida beachgoers are forecast to have stinky conditions in May after a record-setting amount of sargassum seaweed was observed via satellite in the eastern Caribbean Sea and western Atlantic Ocean – more than 200% higher than historical records.
Sargassum is a naturally occurring brown seaweed that floats in large masses across the ocean. When it washes onshore, it decays, creating a foul smell that can significantly impact beach tourism and cause fish kills. This stinky seaweed typically arrives on Florida beaches from summer through fall.
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According to the University of South Florida’s (USF) College of Marine Science Optical Oceanography Lab, South Florida and most Caribbean beaches are expected to see an increase in sargassum in May after a record-setting blob was spotted in the Caribbean in April.
A seaweed belt surrounds boats moored along Dinner Key Marina outside of Monty's Coconut Grove restaurant in Miami, Florida on Thursday, May 8, 2025. Scientists predict 2025 to be a record seaweed season. (Getty Images)
According to USF’s Sargassum Watch System, the total amount of sargassum set a new record in April, exceeding the previous all-time high in June 2022. Researchers say the exact reason for this record-setting amount of seaweed still needs to be investigated.
USF said total amounts of seaweed in the eastern Caribbean Sea and the western Atlantic reached "surprisingly high levels." Both were 200% higher than their historical records for the month, and the combined regions were 150% higher than the historical record for April.
In May, more concentrated areas of sargassum will be transported to the western Caribbean Sea and then to the Gulf through the Yucatán. This means seaweed inundation is possible throughout most of the Caribbean islands and along the southeastern coast of Florida.
A map showing the average Sargassum seaweed for the month of April 2025 with warm colors representing a higher amount in the Caribbean Sea and Gulf. (Optical Oceanography Lab at the USF College of Marine Science / FOX Weather)
USF’s lab recently upgraded its Sargassum Watch System to include the coastlines across Florida and the Caribbean. The researchers have also used updated algorithms to forecast the movement of sargassum days in advance.
According to USF, these new tools will help manage the problem before it reaches coastlines, where it decays and releases harmful gases, leading to fish kills.
Drone video: Seaweed covers some South Florida beaches
Drone video taken on Wednesday showed clumps of seaweed covering parts of South Florida’s shoreline.