Sargassum Season Checker

Sargassum season in Cancún ran March to September in NOAA’s daily risk: the coast was rated medium or high on every day of those months, and on 0 of 30 days in November. NOAA: the Caribbean’s sargassum “peaks during the summer months”. Pick your beach for today’s rating.

How to use it

Pick your beach, then leave When on The newest rating to see what NOAA said most recently, or pick the month of your trip to see how that month went in each year of the record. The bars show all twelve months at once; the strip shows the last 30 days; the list names the calmest beaches that month. Every number is a count of NOAA’s days, from July 1, 2025 to September 27, 2026.

What NOAA’s rating is

The Sargassum Inundation Risk (SIR) is made every day by NOAA’s Atlantic Oceanographic and Meteorological Laboratory with the University of South Florida. “Using as core inputs the AFAI (Alternative Floating Algae Index) fields generated by the University of South Florida (USF), the algorithm analyses the AFAI values in the neighborhood (50-100 km) of each coastal pixel and, computing the difference between those values and a multiday baseline, classifies the risk into four categories: low (blue), warning (yellow), medium (orange) and high (red).” “In black are areas with not enough data.” And “SIR shows the current conditions of Sargassum density and identifies coastal areas where Sargassum is within 50-100 km and, therefore, may potentially be impacted by Sargassum in the following days/weeks.”

So it is a risk from satellites, not a beach report: a medium or high rating means sargassum was close offshore and could wash in, not that the sand is covered today. The planner gives each beach the highest rating NOAA gave any stretch of coast within 10 km of it that day; a day too cloudy to rate is counted apart, never as low.

The season

“Since 2011, large amounts of Sargassum is a recurrent problem in the Caribbean Sea, in the Gulf of America and tropical Atlantic.” From NOAA’s sargassum FAQ: “There are two main sources of Sargassum reaching the Gulf of America, one is local and peaks in April-May, and the second one is the Caribbean Sea which peaks during the summer months.” “During the late winter and early spring months, the Sargassum moves northward with the seasonal winds and currents.” “The motion, extent, and density of Sargassum is very complex – it grows, sinks, and moves according to ocean currents, winds, and waves.” And “Sargassum outlooks are published once a month by the University of South Florida.”

Every beach, month by month

The share of rated days NOAA called medium or high, July 1, 2025 to September 27, 2026 (July to September count two years, the other months one).

Worked examples

Cancún in July. Medium or high on 61 of 61 days. The calmest beaches here that month: Clearwater (5%), Nassau (10%), South Padre Island (11%).

Punta Cana in March. Medium or high on 5 of 31 days, against 31 of 31 days in Cancún: the two coasts do not follow one calendar.

Miami Beach in June. Medium or high on 30 of 30 days; Clearwater, on the Gulf side, 8 of 30 days.

Common mistakes

• Reading a rating as the beach today. SIR rates what is offshore and could arrive “in the following days/weeks”; a beach can be raked clean at dawn under a high rating.
• Trusting one year. The record here is 454 days; NOAA’s FAQ calls 2025 “a new record year”, so a normal year may be lighter.
• Forgetting the other side of the island. Cozumel’s and Isla Mujeres’ west shores face the mainland and the east shores the open sea; the rating covers the coast within 10 km, both sides.
• Taking a cloudy day as a clean one. A day NOAA could not rate is shown as too cloudy, not as low.

Plan the trip

Read things to do in Cancún, things to do in Playa del Carmen, things to do in Punta Cana, the Puerto Rico travel guide, the clearest beach in Key West and things to do in Aruba. Then check Cancún’s rainy season, its hurricane season, the best time to visit and Florida’s beach conditions today.