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Sargassum 2024

Key West sargassum 2023 | Four months early and already piling up

By Linda Grist Cunningham, editor and proprietor

Linda Grist Cunningham is editor and proprietor of Key West Island News and KeyWestWatch Media LLC. She and her husband, a park ranger at Fort Zach, live in Key West with their Cat 5s.


No. Just no. It’s not time for the Key West sargassum 2023 update. I don’t write about Key West sargassum until June; heck maybe not until August. So, one beautiful Saturday morning back in mid-February, out on an Argo Navis sail with the Key West Art and Historical Society, I pretended I didn’t see those lovely floating patches of golden sargassum.

I mean that’s a summer thing, right? And, then last week I happily reassured a visitor planning to bring his kids to Key West in June for a few beach days that he could be reasonably certain early June’s shoreline and waters would be fine. Maybe some patches, but not piles.

And. Then. Came. Monday. Monday I drove around South Roosevelt toward the airport on my way up the Keys. Mary, Joseph and the Wee Donkey, the beach rake tractor was cleaning Smathers and the sargassum was an undulating carpet of gold and brown along the shoreline.

It was the same last week at Fort Zachary Taylor State Park. The same up on Geiger Key along the channels. There’s not enough right now to overwhelm the beaches. The weather remains cool enough that the mid-summer stench of rotting sargassum is held at bay. And the winter winds are changeable enough that a lot of sargassum gets pulled back out to sea and away from the beaches.

Make no mistake. Key West’s 2023 sargassum season will be longer than in the past and likely as bad as last summer’s. The University of South Florida, which monitors the sargassum flow, in early February made this prediction:

Looking ahead, the decrease in sargassum quantity from January to February is uncommon, and
presents a glimmer of hope that the overall 2023 bloom may not be as large as previously feared,
although 2023 will still be a major sargassum year. Nevertheless, the large quantities already in the CS (Caribbean Sea)
(and to the east) will continue to accumulate and migrate, creating beaching hazards along
the way. The Florida Keys may start to see small amounts in March.

We can amend that prediction right now: We have already seen not just “small” but large amounts in March.

Key West sargassum 2023
Sargassum floats at the Fort Zach shoreline on March 4, 2023. We usually don’t see this much until late spring.

Key West sargassum 2023 | What to expect

So. Now what? Let’s do a quick sargassum primer.

Sargassum is a form of brown algae that floats on sea water and never attaches itself to the sea floor. Don’t confuse it with sea grass, those long, waving grassy patches that grow in the sand under water. Sargassum itself is not harmful to humans — unlike red tide and blue-green algae, both of which are out of control in other parts of Florida, but not so much in the Keys. (It’s the hydrogen sulfide from decaying sargassum that causes respiratory problems.)

We are seeing red tide in Monroe County these days, unfortunately, which means we are becoming increasingly vulnerable. Florida Fish and Wildlife monitors red tide and said last week it was monitoring one offshore bloom up the Keys. You can follow along at the FWC website.

Decomposing sargassum releases an intense “the devil has arrived” sulfur smell. That’s hydrogen sulfide. It stinks, but generally doesn’t harm humans in outdoor settings. (Although, if you’re sensitive to strong smells or have significant respiratory problems, like asthma, you might want to wear a mask or limit your exposure until you see if the hydrogen sulfide bothers you. I’ve found that after a few minutes I don’t smell it anymore and it doesn’t trigger my asthma. But, there’s growing scientific research that huge quantities of hydrogen sulfide, even outside, may be a bigger health threat that we thought.)

If you walk or swim through sargassum it feels like you’re being tickled with soft brushes. If you think you’ve been stung, it’s because tiny animals and organisms that call sargassum home are peeved at your intrusion and they sting. Sargassum is critical to the ocean’s ecological systems. It’s a nursery for sea turtles and assorted fish and saltwater species.

Scientists and researchers are busily trying to come up with smart (and profitable) ways to use all this excess sargassum. Ranger Ed and I are getting ready to do our own science experiment this spring, using sargassum compost in our planting beds. The trial compost was developed by the Key West Tropical Forest & Botanical Garden. You have to be careful with sargassum compost because sargassum contains a hefty load of heavy metals like arsenic, which is super harmful to plants and humans. I’ll let you know how it goes.

Summer has always meant sargassum. What’s worrisome these days is the escalating quantity and the fact that the sargassum blooms are no longer limited mostly to the Sargasso Sea. Instead, the historic blooms are being supplemented likely fed by massive nutrient runoff from the destruction of the rain forests along the east coast of South Africa — and from our own excessive nutrient runoff from mainland Florida and the overburdened Keys ecosystems.

Key West sargassum 2023 | What you really want to ask

But the question you really want to ask is this one: What are the beaches and the water going to be like for summer vacation? Before I offer up my predictions, a definition: Sorta OK means visible sargassum on the beach, stinky air and sludge-like dead sargassum in the water at the shore line. But, sorta OK also means you can enjoy the beach and walk out far enough from shore to find clear water.

Here are my predictions:

Smathers and Higgs will be sorta OK because the city and county clean them sorta. Fort Zach will be decently OK because even though the state doesn’t clean it, the current tends to pull the worst out to sea and away from the beach. South Beach will be a mess unless the city and the private developer get the barricades proposed last year built. Dog Beach could be dicey, but the dogs don’t care. Bahia Honda might be challenging because the state doesn’t clean the beaches and they are positioned perfectly to catch the sargassum.

Up the Keys? I’m not nearly as familiar with sargassum up there; those beaches are a 100 or more miles from me. But Atlantic side likely will have more than Gulf side. Resorts up there with beaches are likely to do at least some cleaning and raking.

And, yes, I’d still come to Key West because, let’s face it, no one really comes here for the beaches. Go to the sandbars instead.

Month by month predictions

Sidebar to those who are asking about specific dates: I love that you’re interested and concerned about your plans. I totally get it and I wish I did have a crystal ball. I don’t have any way of knowing what things are going to be like or what your expectations and tolerances are. You’ll need to make your own decisions. The Keys and Key West are magical places, so, honestly, sargassum isn’t likely to completely ruin most folks’ vacations. Fact is, I’ve long said, “If you’re coming here for the beaches, you’ll be disappointed. The best beaches in Key West are in Pensacola.”

Here’s what I predict by month for the Atlantic side of Key West. Always subject to change and can vary widely as one goes east up the Keys and depending on whether you’re Gulf side or Atlantic side. Up the Keys, the Gulf side will likely have less, maybe none, because the Atlantic side catches it. My predictions are based on my personal experiences, mostly in Key West, over the past decade-plus. As they say it the financial world: Past performance is not a guarantee of future performance. Plus Mother Nature laughs at me when I predict things:

March and April: Not much to worry about. Forget about the worries and come on down.

May and June: More, but if it’s not too hot and the currents are right, probably you won’t notice much. Don’t get nuts and do crazy things like reschedule for September, October, even November. That’s the height of hurricane season and a hurricane beats sargassum, hands down. Come on down in May and June, and pretty much you’ll be fine.

July, August, September: Summer heat and humidity combine with beached sargassum and some days — though not all — can be stinky with pudding-like nearshore waters. Beaches on the Atlantic side without good currents can trap sargassum, which may or may not get cleaned up. Daily clean-up may not be enough. In deep summer it’s getting tough to keep up with sargassum beaching. Summer heat means decaying beached sargassum that’s hard clean up and significant smell. It’ll likely be decent out on the sandbars and likely decent for water sports well off shore. And, if you’re not here for the beaches, which most folks are not, then who cares?

September and October: The height of hurricane season. We’re not worrying about sargassum; we’re getting emergency prep done and putting up shutters. You probably don’t want to be here for one of those, for sure.

Want to know more about Key West sargassum?


  1. Roger Horn

    My wife and I came to KW for the first time this past December for our retirement trip and fell in love with the area. We have another trip already booked this this coming December. Should we be worried about the sargassum problem? The weather channel has brought it up a lot but they typically blow issues out of proportion.
    We will be very close to Higgs Beach (Key West Beach Club).


    • Linda Grist Cunningham

      You’ll be fine in December. Sargassum is a challenge during the summer months.

  2. John H Shinn

    We are a senior couple who live in Delaware but have loved our trips to Key West. Since it has been almost 20 years since our last journey to your world, we want to have one more great adventure in Key West and we were planning on late July. But alas, the sea weed is all we hear about and you are most vocal and detailed in reporting it. (Thank you for that info.) Your reporting is great and I’m glad I came across it.
    But the bottom line is : Should we stay or should we go?

    • Linda Grist Cunningham

      Ranger Ed and I are a senior couple and we love Key West in July. Heck, we love Key West no matter what. Let’s start with the sargassum. It’ll be piled high along the water’s edges and likely the water will be chocolate pudding that you’d have to wade through if you decided to go for a swim. (I just don’t do that mess, I’ll admit.) But, I’m guessing you’re not planning to train for an Olympic ocean swim, so sitting on the beach, loving the view and enjoying the day? That’ll be fine. It WILL smell, but this I guarantee: About three minutes (max) and you won’t smell it. The nose does that for us (thank you, Nose) and unless you take a big whiff of, say, Cuban coffee, which will clear the nose and you have to start all over again, you won’t be bothered. So, if it’s sargassum and the smell you’re concerned about? Come on down; you’ll be fine. It will be hot, humid and everything will stick to your skin. Your hair will be straggly, which is why we all wear hats. Well, that, and the fact that we don’t have as much hair as we used to and the hat protects our bald noggins from the sun. It will be 89 at midnight and 92 at noon. But, we do have air conditioning, which makes July manageable. Fingers crossed, it won’t be high-season crowded and there won’t be a whole slew of family vacationers. Covid years brought us an inordinate number of visitors in the summers, so it’ll be busier than your memories. And, 20 years brought us a lot of traffic, way too many cars, golf carts e-bikes and assorted other modes of transportation. There are bunches of folks who lament today and long for the olden times. I’m not one of them. And, having said all that, I leave you with this: No matter when one encounters Key West, the magic remains. You may have to hunt a bit, but it’s there. Stay or go? By all means, come to Key West in July. If you love the island, it will most certainly love you back.

    • Lori

      Does all of KW stink or just near the beaches?

      • Linda Grist Cunningham

        Actually, there’s no smell right now from decaying sargassum. That’s because the huge sargassum bloom expected this summer was blown apart by two hurricane-level storms early in the summer. But. Our record-breaking heat is sure churning some nasty smells from garbage cans.

  3. Jen Williams

    Thank you Linda for the very informative read. Coming in May 2023. Have had my week long trip to The Keys planned since October 2022, and cannot wait to be there. Snorkeling, sunshine, swimming, kayaking, sunsets, food, drinks, music, arts, shopping, nature… no place I would rather be, with or without the seaweed!!

    • Linda Grist Cunningham

      With or without! I completely agree.

  4. Andrew M

    This is helpful, thank you! Do you have any insight on whether or to what extent it will affect fishing (specifically in May)?

    • Linda Grist Cunningham

      Great question, Andrew. I’m not a fishing expert, but from what I hear and in May, there ought not be much problem. Much later in the summer when the huge mass is floating out on open waters, I know captains will be concerned about getting caught up in it. But the experienced ones will know where to go — and, better still, not to go.

      • Polly KC

        Hi Linda – Thank you for the detailed information. We have planned to visit Key West in a couple of weeks and are looking at staying alnear Smathers Beach or near the Southernmost resort beach. We are prepared for the sargassum but is one better than the other in terms of cleaning it up? Thank you

        • Linda Grist Cunningham

          Both are city beaches so there is some cleanup of the beaches. Smathers is the bigger of the two with more sandy area and more open water. South Beach is very small and it tends to catch and hold sargassum. But, I can’t predict what things will be like in a couple weeks. For instance, the wind shifted from north to south late this week and we saw sargassum beaching for the first time in several days. The sargassum status totally depends on wind direction, currents and how warm the air temperatures are. So, if I were choosing a location, I’d do it based not on the beach, but on what I planned to do while I was here. South Beach is close to everything that folks usually come to Key West for. Smathers isn’t.

    • Todd

      I have wondered…are these blooms larger because they are helping absorb a lot of the nitrogen and so forth in the water that we have caused to be there? We’re feeding them. If we reduce or eliminate these blooms, will it cause other ecological problems because the blooms of algae won’t be doing enough in reduction?

      • Linda Grist Cunningham

        We definitely need sargassum as a significant part of the ocean ecosystems. Eliminating sargassum would be devastating to turtles, fish and other sea creatures who live within them. The problem now is quantity. If there were a way to reduce the out-sized bloom, I suspect that would be a good thing.

  5. Kristen Mullen

    Linda- first, thank you, this is so helpful! I’ve been seeing the resent news about the “5,000 mile wide blob of sargassum” and it’s concerning. My boyfriend and I will be in Key West very soon- the last week of March. My concerns are will the sargassum affect boating, either getting tangled up in the motor, as well as at the sandbars will there be a lot of seaweed floating around etc? Also do you believe the stench be noticeable inland or primarily on the beaches? We are staying at The Marker. Thanks in advance!

  6. Trish Tagle

    Planning a trip late April 2023 on Smathers Beach. Hoping to enjoy the beach and snorkel. It is already stinky? Should my family still come?

    • Linda Grist Cunningham

      I’ve added a new section to the original column with my by-the-month predictions. You may find that helpful as you make your plans. Late April? Smathers? Should be OK; will depend on how the winds, currents and temps are between now and then. Snorkeling off Smathers isn’t all that smashing any time of the year. If you want off-the-beach, maybe try Higgs along the pier or along the White Street Pier.

  7. Elizabeth Dietz

    Hello Linda,
    My husband and I, along with our two teens, have a trip planned for the week of April 10th. Our home base will be in Marathon on the Gulf side, at Tranquility Bay but we really wanted to explore throughout the each of the Keys. I understand about the crystal ball, but your best guess… do you think we will be disappointed and affected by the sargassum? Since that would really stink, no pun intended, should we consider postponing our trip until November? We have another opportunity to take the time then if that’s a better option.
    Thanks so much.
    Elizabeth D.

    • Linda Grist Cunningham

      I think y’all will have a wonderful trip. April is lovely and you shouldn’t see much, if any, sargassum problems, especially since you’re on the Gulf side.

  8. John Doxey

    Hi, First time at your site. Any tips on the best places to get information about sargassum at other places up and along the Gulf Coast? We’re headed to Pensacola (Perdido Key) April 23rd.

    We planned to go to Key West a few years ago but a hurricane derailed our plans. I had been there years before and the ride down from Miami was beautiful. Had been talking to my wife about it for years. We’ll get there some day.


    • Linda Grist Cunningham

      John, I’ll hunt around, but off-hand nothing comes to mind. I can’t recall sargassum being a problem that far north in the Gulf of Mexico. The currents likely just don’t take it there. The interactive monitoring map I keep handy doesn’t include the Pensacola or any of that part of the Gulf. It’s fun and interesting to check out.

    • Suzanne Bryant

      Hi! My family has a private beach front home for rent on Islamorada Key on the Atlantic side the last week of July. My parents are not easily mobile so having a home that is right on the beach with access to a pool was ideal. Now I am worried about the air quality and accumulation of dead Sargassum. The house is not cheap so wondering if you would advise to change dates as this looks to be the peak time when the algae bloom is hitting Florida’s Atlantic side.

      • Linda Grist Cunningham

        Sorry, Suzanne, I have no insider knowledge that would let me make that kind of advice. Too far out and my experience is really only with Key West and the Lower Keys. Would I still come in late July? Absolutely. From what you say you’ll spend much of your time at the pool so you’re not really going to need to worry about the beach. But that’s me. I’ve added a new section to the original column with my by-the-month predictions. You may find that helpful as you make your plans.

  9. Natalia

    We have a trip to Key West planned for late June 2023. We wanted to snorkel, see the coral reef and spend time on the water (boat, kayak). Do you think snorkeling excursions will be impacted? Is there a way to plan smartly (book trips in advance or wait to see how independent charters are impacted once there)?

    • Linda Grist Cunningham

      Unfortunately, it’s too early to have any kind of accurate prediction for late June. There’s going to be sargassum; there always is. But how much will be along the shorelines depends on so many variables and it can change day to day. All that said, I personally would go ahead with plans for snorkeling, boating and kayaking. Those activities tend to be out on the water away from the shoreline and local charters know where the best places are to go. It’s the piling up on the shore and in the near shore waters that affect beach time. Out on the water? Let’s put it this way: I have sandbar days planned already planned for the summer. (As I tell everyone, I don’t have a crystal ball, so any predictions are based solely on what I’ve experienced over the years.)

    • Natalia

      Thank you, Linda. Your response is so helpful and much appreciated!

  10. Joe

    Probably (definitely) beating a dead horse here, but I am inexperienced and have never been to the Keys. We planned our first family vacation for the week of June 18 this year. My wife, 7 yr old son, 12 year old son, and I. My sons have never flown and we have our first family flight planned. We have a resort booked on the gulf side of Marathon key. Not only do my kids and wife really want to play on the beach and swim my 7 year old has terrible asthma. We are so excited and I know the pressure we are putting on the trip makes it worse but should we reconsider our trip due to the sargassum from your experience? We never knew to consider it until the news started showing this huge early influx. Thank you for your advice.

    • Linda Grist Cunningham

      Oh, Joe, you and the family are going to have such a great time. First things first: Because you’re staying on the Gulf side, your beach and near shore probably won’t have much sargassum. The Atlantic side of the Keys archipelago catches the brunt of it. Second, your resort is likely to rake and clean whatever beach areas it has. Only decaying sargassum gives off the hydrogen sulfide that can trigger asthma and I’ll bet you won’t see much, if any, where you’ll be. And, finally, mid-June is still early in the season. Would I do it with my own kids and grandkids? You bet. I think you’ll be fine. (As I tell everyone, I don’t have a crystal ball, so any predictions are based solely on what I’ve experienced over the years.)

  11. Ken

    We are heading to Islamorada next week. Staying at Cheeca Lodge. What is the current report on the east side of Islamorada regarding the Sargassum?

    • Linda Grist Cunningham

      I don’t have a crystal ball, but you should be fine. Even though we are seeing very early sargassum, the beaches and the shore waters are fine. Obviously things can change, but I sure wouldn’t worry for now.

      • Ken

        Thank you Linda!!

  12. Shelley

    Do you expect our stay at Isla Bella in Marathon to be affected? We will be staying the last full week of March 2023. If so, will it be stinky in March?

    • Linda Grist Cunningham

      You should be fine. Even without a crystal ball and even though we are seeing very early sargassum, there’s no reason to think there’s going to be any problems this early in the year. We always have seaweed along our shorelines unless resorts and government cleans them, but it’s not much and certainly not worrisome. I think you’ll be fine.

    • Nancy

      My husband and I stayed in Islamorada for a long weekend 3/3-3/6/23. I am sorry to say our getaway was affected by the stench of the saragassum and the human garbage (bottles, cans, etc) that washed in with it on the east coast. The resort seemed to be unprepared to do any mitigation (ie, cleaning the waste out of the mess. It was really unpleasant to sit out enjoying the ocean views. It sounds like you aren’t considering it starting by that point, but unless it washed out last week after we left, it was definitely a negative to spending a lot to fly down and pay for expensive lodging.

      • Linda Grist Cunningham

        SO sorry to hear that, Nancy. You must have caught those beaches about the same time I did. And, yet here we are today after wind and current shifts and all is well. That’s the tough part about predicting; even a slight shift affects things. (And, as for the human stuff? Yeah, makes us wonder why we’re not all more careful with our cast offs.) Hope you will fare better on a future a return visit. Thanks for reading along and updating us.

  13. Dionne Mihalus

    What do you think early June will be like?

    • Linda Grist Cunningham

      Probably decently fine. Would I come in early June? Absolutely.

  14. Diane T

    We have a trip to the keys planned for April 23, 2023 to celebrate my husband’s retirement. Sadly it’s a trip that was postponed for to covid and then an 13 month injury recovery.
    What is the prediction for alligator reef? What about the east cost of the keys? I don’t want to come there if it’s going to smell and make us nauseous the whole trip. TIA

    • Linda Grist Cunningham

      We are seeing early arrival, but as my column says, the winds and a currents are such that most is being pulled away from the shorelines. I think you’ll be fine. If it were me, I’d be happily packing and dreaming.

      • Diane T

        Thank you for your quick reply. We will proceed as planned. And with a little luck we will be able to vist all the keys parks.

      • Craig Kunitsky

        We are planning a trip around the July 4 holiday and staying near Malory Square. My son wants to take a trip to the Dry Tortugas. Do you think they will be cleaned by the National Park Service.

        We plan to snorkel vs. hang out on the beach, and I am curious what the sandbars are that you talk about?

        • Linda Grist Cunningham

          I’ve added a new section to the original column with my by-the-month predictions. You may find that helpful as you make your plans.

          Your biggest challenge may be getting reservations on the Yankee Freedom or other Dry Tortugas charters. Those are often booked as much as a year in advance. It’s rare you can get one on the fly, so best start looking now.

          • Craig Kunitsky

            Thank you. What is your favorite sandbar excursion.

          • Linda Grist Cunningham

            Lazy Dog. But there are lots. Just wander around “the Google.” 🙂

          • Karen Kidd

            Hi I’ve heard seaweed protection barriers are happening at Southern most point resort ?
            Any news on this Linda, from the Uk and find this extremely informative thanks

          • Linda Grist Cunningham

            They were supposed to be installed by now, but the latest I heard from local news folks was installation has been delayed as folks involved figure out costs and how to do it.

        • April Keeton

          I was wondering this as well! We wanted to come 7/26.

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