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Sargassum today: seaweed risk per beach
NOAA's satellite risk of sargassum seaweed for every beach we follow in the Caribbean, Mexico and Florida, data of Mon 5 Oct 2026. Worst first.
Where sargassum lands
Sargassum is a brown seaweed that floats in rafts in the tropical Atlantic. Since 2011 it arrives in large amounts from about March to October, carried west by the trade wind and the current: on the east-facing beaches of the Lesser Antilles, the Dominican Republic, Mexico's Caribbean coast and Florida. Beaches on the sheltered west or south side of an island usually get less of it.
How to read NOAA's risk
NOAA's Sargassum Inundation Risk is an experimental product of NOAA/AOML, NOAA CoastWatch/OceanWatch and the University of South Florida. Every day it compares the floating seaweed that satellites see within 50–100 km of each stretch of coast with the weeks before, and gives the stretch one of four classes. We show them as three words:
- Low (NOAA: low): little or no seaweed near this coast.
- Medium (NOAA: warning or medium): seaweed at sea nearby; some may wash up, depending on wind and current.
- High (NOAA: high): a lot of seaweed nearby; expect it on the beach and brown water at the edge.
- No data: clouds or no coast segment near the beach; we do not guess.
What it cannot tell you: whether a hotel cleaned its beach this morning, or a raft that arrived overnight. It looks at stretches of coast of a few kilometres, not at one beach. Seaweed on the beach is not dangerous to touch, but rotting piles give off hydrogen sulphide (the smell of rotten eggs), which can bother people with asthma.
In Europe and Bali there is no sargassum; there we show the official bathing-water quality where it is published: Is the water clean?