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Key Largo (Pennekamp) Seaweed Risk Index today
The risk of sargassum seaweed on the sand.
SHORESCORE SEAWEED RISK INDEX
Clearing this week: down from 70 a week ago
Patches on the sand and mats in the water are likely. You may have to pick your spot, and there can be a low-tide smell up close.
No red tide effects expected.
Reading from Sep 23, 2026.
The last 14 days
Each bar is one day's index, colored by its band. The lines are the cuts between words.
What the number means
| Word | Index | What it means |
|---|---|---|
| None | 0 to 24 | Seaweed piles are unlikely. |
| Low | 25 to 39 | Scattered clumps along the tide line are possible. Easy to step around. |
| Moderate | 40 to 64 | Patches on the sand and mats in the water are likely. You may have to pick your spot, and there can be a low-tide smell up close. |
| Severe | 65 to 100 | Piles on the sand, mats through the water, and a strong rotten-egg smell are likely. If seaweed ruins a beach day for you, pick another beach today. |
About the index
The ShoreScore Seaweed Risk Index is our own 0 to 100 number for the risk of sargassum seaweed washing up on this beach's sand. Higher means a bigger chance of seaweed. The word comes from the number, nothing else. We checked it against a summer of daily beach photos.
It is a risk, not a count: cleanup crews and the waves move seaweed around, so the sand can look better or worse than the number. It is a reading, not a forecast, and the newest reading can be a day or two old. The date under the number says which day it is from. How our numbers work
About sargassum
Sargassum is a floating brown seaweed that drifts ashore from the Atlantic in pulses, heaviest from roughly May through August. At low risk, any seaweed is usually scattered clumps you can walk around. At severe risk, thick mats along the waterline, a sulfur smell as it breaks down, and tougher entry into the water are likely.
ShoreScore folds this reading into Key Largo (Pennekamp)'s overall ShoreScore alongside live weather, surf, and official water quality testing, so one number tells you whether it's worth the trip.
Seaweed Risk Index at nearby beaches
| Harry Harris Park (Key Largo South) | 49 | Moderate· clearing |
| Islamorada (Anne’s Beach) | 33 | Low· clearing |
| Cape Florida / Bill Baggs | 54 | Moderate· clearing |
| Key Biscayne / Crandon Park | 47 | Moderate· clearing |
| Virginia Key | 47 | Moderate· clearing |
Questions people ask
- What is the ShoreScore Seaweed Risk Index?
- Our own 0 to 100 number for the risk of sargassum seaweed on the sand. Higher means a bigger chance of seaweed. It is a risk, not a count, and a reading, not a forecast.
- Is 48 a lot of seaweed?
- 48 is Moderate. Patches on the sand and mats in the water are likely. You may have to pick your spot, and there can be a low-tide smell up close. That is the second highest band.
- Does the number mean the beach is closed?
- No. It is not a warning or a closure. It says how likely you are to find seaweed on the sand. For closures and advisories, check Monroe County and the lifeguard stand.
- When is the number from?
- The date under the number is the reading it uses. It can be a day or two old.
- Does seaweed change the ShoreScore?
- Yes, a little. Seaweed lowers the beach's ShoreScore, but the ShoreScore is a separate 0 to 100 number where higher is better. This page's number is the other way around: higher means more seaweed risk.
Informational only, not for safety decisions. Lifeguards, beach flags and official notices come first at Key Largo (Pennekamp), whatever the number says.