Sargassum in the Riviera Maya: when it comes, where to swim

When is sargassum season in the Riviera Maya?

The pattern is real and the calendar is only half the answer. Every dated figure below comes from the state's own reports, the Navy's bulletins and the satellite lab that tracks the belt, read on 25 September 2026.

On a bad morning the brown band sits where the turquoise should be. A crew works the waterline with hand tools, and the sea past the barrier looks perfect. That week lands somewhere on this coast most years now, and it has a shape: inside the Atlantic belt that formed in 2011, sargassum peaks in June or July. ¹

Before 2011 the seaweed mostly stayed out at sea. It lived in the Sargasso Sea and the Gulf of Mexico. Then its range widened into one continuous belt from West Africa to the Gulf, and Caribbean beaches began receiving it in quantity. NOAA now runs a satellite Sargassum Inundation Report that scores the chance of landfall within 50 km of a coast on three levels. ^{1, 10}

The month sets the odds and the wind picks the week. USF, the lab behind the satellite tracking, measures how much floats offshore and says beach-level landfall stays hard to forecast. Wind, swell and currents put the mats on one coast and spare the other. That is how two beaches in the same state read green and red on the same morning. ^{1, 3}

How much seaweed did 2026 actually bring?

2026 is the heaviest year Quintana Roo has counted. Federal authorities put the January to 27 August total at 90,548 tons, the highest year-to-date figure in about six years of monitoring. Eight days later the count passed 123,000 tons. Work out the gap and it comes to 32,452 tons in eight days, about 4,056 tons a day, along the beaches of one state. ^{12, 2}

The beach-level version of that tonnage is older and starker. USF recorded hotels along this coast removing 1,000 to 10,000 tons per kilometre of beach during the peak months of 2018 and 2019, across seven beaches. That is the scale a peak reaches when the mats arrive faster than anyone can catch them offshore. ¹

Then it eased. On 27 August 2026 the Navy cut its Quintana Roo alert from red to yellow, with arrivals well below the May and June peak, while still forecasting 17 tons for Puerto Morelos and 16 tons for Xcacel, a state-protected turtle sanctuary, within 24 hours. Industry voices in the same report expected roughly two more months before Playa del Carmen's water fully cleared. ¹²

USF's own August outlook agreed, with one caution. Volume fell in every region that month and still sat above the 75th percentile of historical levels everywhere except the east Atlantic. The lab expected the decline to carry on through the following months, possibly until November. ¹

Where the water stays clear: the north and the islands

This coast splits north and south, and the split is wide. On 22 September 2026 the state's monitoring covered 140 beaches. In the 100-beach northern zone, 62 were clear or lightly touched and 16 were abundant or excessive. In the 40-beach southern zone, 6 were clear or light and 29 were abundant or excessive. Same state, same morning. ⁹

Isla Mujeres and Holbox are the north's strongest card. On 18 June 2026, deep in the peak, Playa Norte, Playa Centro and Punta Sur on Isla Mujeres read green or blue, and Holbox held nil to very low levels. The same report put southeast winds of 30 to 40 km/h and a 1.9 m swell behind the seaweed piling onto the southern coast. ³

Tulum and Akumal face the belt directly, with no island to break it. This stretch reads yellow more often than green: on 15 March 2026, Cancún and Puerto Morelos held green while Tulum, Akumal, Playa del Carmen and Mahahual all read yellow. ¹¹ Xcacel, the turtle sanctuary between Akumal and Tulum, was one of two beaches the Navy named on 27 August 2026, with 16 tons forecast within 24 hours. ¹²

Is Cozumel clear of sargassum?

Cozumel's problem sits on the east coast, the side almost nobody sleeps on. Zofemat, the municipal authority for the federal shoreline, works the eastern beaches every day: the Chumul lookouts and Chen Río, 6 to 10 tons lifted daily across as much as 700 linear metres, by 54 people with hand tools. Turtle nests and environmental rules keep the machines away. ⁴

Which leaves the west side, where the town, the ferry and the dive boats are, usually clear. Usually carries weight here. Arturo Can Novelo, Zofemat's director in Cozumel, set out the east-coast work to Heraldo de México on 18 August 2026, the day the island held a yellow alert. The same report describes an irregular storm dumping 15 tons on the west-facing malecón the week before. ⁴

March 2026 is the reminder. Over the weekend of 15 March, monitoring portals put El Naranjal, Xcalak and Isla de las Golondrinas on red. Among eight beaches rated moderate between Tulum and Cancún that weekend was El Cielo, Cozumel's shallow snorkelling spot. Seaweed in a quiet month, on the island's calm side. ¹¹

Sargassum is a surface problem, and that shapes the plan. It floats, and it piles where water meets sand. ^{1, 10} A shore snorkel is the morning a red flag spoils; a boat day offshore is the one that usually survives. Price both before you book: MMT's Cozumel diving budget covers the boats and the beds, and the marine park fees are a separate line.

When is the best time to visit Cancún?

Book outside June and July and you cut the odds. That is the whole of the seasonal advice the evidence carries. The Atlantic belt peaks in those two months, and USF expected 2026 volumes to keep falling into the autumn, possibly until November. Winter and early spring brought the lighter reports this year: on 15 March, Cancún and Puerto Morelos both read green. ^{1, 11}

• December to April looks like the lower-risk window on 2026's reports, with Cancún and Puerto Morelos green in mid-March while the far south ran red. ¹¹
• May to August is when the belt arrives. The Navy's alert stood at red through the May and June peak and came down to yellow on 27 August. ¹²
• September and October are recovery, not clarity. On 22 September 2026, 135 of 140 monitored beaches still carried sargassum, and the Navy planned to take vessel operations down to 70 percent of capacity between late September and early October. ^{9, 2}
• November closes the cycle in a declining year. USF's August outlook expected volume to keep dropping in every region, possibly until that month. ¹

One caveat sits under the calendar. These windows are odds drawn from one heavy year's reports, and the wind still picks the week. Anyone booking a beach-first trip in June should treat the daily bulletin as part of packing and hold a plan for a red morning. ⁵

How do you check today's beach report?

Two official sources, both free. Mexico's Navy, through its Instituto Oceanográfico del Golfo y Mar Caribe, has published a daily sargassum bulletin for the Mexican Caribbean since 2019, with today's edition and an archive behind it: Semar's bulletin page. USF's lab issues a regional outlook by the last day of each month on its Sargassum Watch System page. ^{5, 1}

The beach-by-beach layer belongs to the state. Quintana Roo's environment secretariat runs a monitoring centre inside the state's C5 command hub, reading imagery from European Space Agency satellites to rate more than 140 beaches and publish daily forecasts. Those ratings are the colors behind every snapshot on this page. ^{6, 9}

The maps travellers actually open are citizen projects. On 25 September 2026, sargazo.info listed 74 monitored beaches across 10 Quintana Roo towns and called 42 of them clean that day: sargazo.info. Sargassum Monitoring, a Texas-registered nonprofit, has gathered crowdsourced photos and reports in more than 43 countries since 2018. Both mix community reports with official data, and say so. ^{13, 14}

1. 01

   A week out, read the month

   Open USF's outlook for the regional picture. The lab publishes it by the last day of each month, and it tells you which way the season is heading. ^{1, 5}

2. 02

   Two days out, read the Navy

   Semar's bulletin page carries today's edition and the archive back to 2019. This is the official Mexican answer for the Caribbean coast. ⁵

3. 03

   The night before, read the colors

   Find your beach in the day's state ratings and match the color to the table above. Green and blue mean swim; orange and red mean move. ^{7, 9}

4. 04

   In the morning, read a citizen map

   sargazo.info and Sargassum Monitoring add photographs and reports from people standing on the sand. Treat them as the third opinion, after the two official layers. ^{13, 14}

770 million spent, 2,000 million promised

Two governments are spending here at once. On 30 July 2026, Quintana Roo's governor said her administration had invested more than 770 million pesos in an integrated sargassum response. The same day, Mexico's Navy secretary set out a reinforcement worth more than 2,000 million pesos in two stages: more collection vessels, more containment barriers, more equipment for the beaches. ¹⁵

On the sand, that money reads as barrier metres. Playa del Carmen opened 2026 with 2,600 metres of marine barrier, reached 5 kilometres by February, an extra 2,400 metres, and by September the Navy was studying up to 10,000 metres more, pending work on currents, winds and tides. The national strategy runs in five stages: monitoring, collection in open water, coastal collection, containment by barrier, and beach cleaning. ²

Catching it at sea is the part that shows. Of the 123,000-plus tons collected by 4 September 2026, more than 50,000 came from Navy work, about 41 percent, and roughly 20,000 tons were lifted out of the water before reaching a beach, about 16 percent. Every ton stopped offshore is a ton that stays off the sand. ²

Build the week so one red beach costs you nothing

The money question under all of this is refundability. A beach that turns red for three days changes a snorkel plan, a boat day, sometimes a hotel. What it costs you depends on the terms you agreed to. Book the flexible version of anything that depends on the sand, and read the cancellation wording before you pay: MMT's guide to what is actually refundable sets out the questions to ask.

• Sleep north, travel south for the day. Isla Mujeres and Holbox held green and blue through the June 2026 peak while the southern zone ran red on 37 of its 40 monitored beaches. ³
• In Cozumel, stay west. The crews, the tonnage and the hand tools are all on the east coast. ⁴
• Put the boat morning in the heavy week. Offshore water is the part sargassum leaves alone; the shoreline is the part it takes. ¹
• Keep one day loose, away from the sand. A red morning is easier to absorb when something inland is already on the list.
• Ask the hotel what it does on a red day. Hotels along this coast were removing 1,000 to 10,000 tons per kilometre at the 2018 and 2019 peaks, so the answer exists somewhere in the building. ¹
• Set the wider budget first. MMT's Mexico travel guide covers the regional routes and the arrival day this decision sits inside.