Data

Sargassum this week in the Caribbean

6 of 21 destinations read above their own norm for the date, 4 near it and 11 below it.

Updated 31 Oct 2026 · Satellite week ending 30 Oct 2026 · License: CC BY 4.0

Every island against its norm

Island	This week	Norm	Times its norm	Reading
Tulum	14.3%	8.9%	1.6×	Above its norm
Punta Cana	7.1%	4.7%	1.5×	Above its norm
Bahamas (Nassau)	1.2%	0.8%	1.5×	Above its norm
Bahamas (Harbour Island)	0.8%	0.5%	1.4×	Above its norm
Dorado	1.9%	1.4%	1.4×	Above its norm
Bahamas (Exuma)	0.8%	0.3%	Norm too low	Above its norm
Jamaica (Montego Bay)	3.3%	3.2%	1.0×	Near its norm
St. Lucia	1.6%	1.8%	0.9×	Near its norm
Antigua	0.8%	0.9%	0.8×	Near its norm
St. John	0.8%	1.0%	0.8×	Near its norm
St. Barts	0.4%	0.8%	0.5×	Below its norm
Grand Cayman	0.4%	0.8%	0.5×	Below its norm
Curacao	0.4%	0.9%	0.4×	Below its norm
Mustique	0.4%	1.8%	0.2×	Below its norm
Anguilla	0.0%	0.6%	0.0×	Below its norm
Aruba	0.0%	1.1%	0.0×	Below its norm
Barbados	0.0%	1.6%	0.0×	Below its norm
Grenada	0.0%	1.7%	0.0×	Below its norm
St. Martin	0.0%	0.6%	0.0×	Below its norm
Virgin Gorda	0.0%	0.6%	0.0×	Below its norm
Turks and Caicos (Providenciales)	0.4%	0.5%	Norm too low	Low, like its norm

For the picture across the year, see the sargassum season by island. For forecasts, the University of South Florida runs the Sargassum Watch System.

Use these numbers

Quote it

In the week ending 30 Oct 2026, 6 of 21 Caribbean destinations read above their own norm for sargassum, among them Punta Cana at 1.5 times its usual level for the date, according to Gladori’s reading of NOAA satellite data.

Full citation:

Gladori, Sargassum this week in the Caribbean (2026), https://gladori.com/data/sargassum-this-week/. Updated 31 Oct 2026. Sargassum data: USF AFAI via NOAA AOML.

Download it

Every weekly reading (CSV)

Free to reuse under CC BY 4.0. Each file carries its sources in the first lines.

Does this tell me if my beach has sargassum?

No. Each number covers open water in a box about 70 miles (110 km) wide around the island, and satellites miss the last stretch next to the shore. One bay can be clear while the next one fills up, because wind and currents decide that.

What does "its norm" mean?

The average signal for the same dates of the year since 2018, for that island. An island with little sargassum in October has a low norm, so even a small rise can put it above.

Why do some islands have no multiple?

When the norm is under 0.5%, a few pixels can double the ratio with nothing real behind it. Those rows show both percentages and no multiple.

How often does it change?

The satellite fields are 7-day composites that NOAA updates daily. We read the newest one on each run, and we keep every reading in the history file.

Method and limits

The number is the share of clear sea pixels in a box about 70 miles (110 km) wide around each island where the floating algae index reads above zero, in the newest 7-day composite.
The norm is the mean of the same measure on earlier composites within 7 days of this date of the year, from 2018 on. A week and its norm are measured the same way.
A reading with too few clear pixels shows as too cloudy. A multiple only appears when the norm is at least 0.5%.
Above 1.25 times the norm counts as above, and 2 times or more as well above. Under 0.75 times counts as below.
The signal compares islands and dates. It is not tonnage, and it says nothing about one beach on one day.
The sargassum data is not intended for legal use, so these figures do not support a claim or an insurance case.

Sources

Source	What it gives	Terms
USF AFAI via NOAA AOML	7-day floating algae index, updated daily	May be used and redistributed for free. Not intended for legal use. No warranty from the contributor, NOAA or the US government.