Sargassum is a type of brown floating seaweed that naturally drifts through the ocean, providing an important habitat for marine life but sometimes accumulating along coastlines in large amounts. In recent decades, sargassum has shifted its range — thinning out in the North Atlantic’s Sargasso Sea while expanding throughout the tropical Atlantic. This trend, which began in 2011, continued in 2026, with the algae reaching its annual peak in June across the Great Atlantic Sargassum Belt and both the Caribbean Sea and Gulf of Mexico experiencing record-high levels.
That said, sargassum conditions can change week to week, so it’s best to check Belize forecasts, NOAA/AOML reports, and local operator updates before traveling — especially during peak season (June–October). Live map links and local forecasts are provided below to help you monitor conditions as your trip approaches.
Sargassum seaweed is a free-floating brown seaweed that originates in the Sargasso Sea and the equatorial Atlantic. Since 2011, a weather pattern shift has caused enormous quantities to wash into the Caribbean, including Belize’s coastline, each year. That geography, where Belize sits in the Caribbean, is exactly why east-facing beaches catch the drift each summer while inland Belize never does.
Historically, the majority of Sargassum aggregated in the Sargasso Sea in the western North Atlantic, with some small amounts found within the Gulf of America and Caribbean Sea. In 2011, the geographic range expanded, and massive amounts of Sargassum moved west into the Caribbean Sea, Gulf of America, and tropical Atlantic, washing ashore in Florida, Puerto Rico, the US Virgin Islands, and most islands and coastal areas in the Caribbean Sea and Western Africa.
The main season runs roughly March through October, peaking June to August. Arrivals vary week to week with wind and currents, which is exactly why a live map beats a static seasonal chart. For month-by-month planning, see our full Belize sargassum guide.
Exposure varies dramatically by location. The barrier reef, prevailing winds, and beach orientation determine how much sargassum any given stretch receives, from Ambergris Caye and San Pedro in Belize to Hopkins and Placencia. Here is the honest regional picture.
Since 2011, large accumulations of Sargassum have occurred every year in the Caribbean Sea, Gulf of Mexico, and tropical Atlantic, but the amount can vary from year to year.
The presence of Sargassum occurs over large areas from the tropical Atlantic in the east to the Gulf of Mexico in the west, approximately 5,000 kilometers from the eastern tropical Atlantic to the west off the Mexican coast in the Caribbean Sea. Sargassum does not extend as a blanket (or blob) covering the full surface of the ocean in these regions. Instead, Sargassum floats in patches that range in size from a few centimeters to hundreds of meters. Some of these patches reach the coastal areas, including beaches, ports, and even intake systems for drinking water. The area that these patches cover has been significantly larger in recent years than prior to 2011.
Satellite sensors can estimate indicators related to Sargassum coverage, which enable us to quantify the area affected and estimate the volume of Sargassum in a specific region.
Out at sea, Sargassum is an important habitat for fish, sea turtles, and other marine organisms, but as it accumulates close to the coastlines it can smother valuable corals, seagrass beds, and beaches. As it washes ashore the seaweed begins to decay, attracting flies and other insects. Additionally, during its breakdown, Sargassum produces hydrogen sulfide gas, which smells of rotten eggs, repelling beachgoers and affecting the tourism industry that depends on pristine ocean conditions. Sargassum can also impact navigation, block water intake in desalination plants, and impact benthic ecosystems after/if they sink to the bottom of the ocean.
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