How far offshore is the Gulf Stream from the Florida Keys?

It moves. The Florida Current, the start of the Gulf Stream, runs along the outside of the Keys reef line, sometimes a few miles past the reef and sometimes much farther out. That is why a daily satellite map beats a fixed number.

How do you find the Gulf Stream edge?

Look for the place the water warms and turns bluer over a short distance, often with weed lines, rips and birds. On a satellite temperature map it is the line where the temperature changes fastest; Fish Scouter traces that line each day off the Keys and Southeast Florida.

What fish live on the Gulf Stream edge?

Dolphin (mahi) work the edge and the weed lines, sailfish run the 100 to 150 ft reef edge in winter, blackfin tuna and amberjack gather on the deep humps, and wahoo hunt the drop-offs. Swordfish are fished by day on the bottom in very deep water past the drop.

Can you see the Gulf Stream edge in summer?

Often not on a temperature map. In high summer the whole Straits can sit at nearly one temperature, so the edge disappears from the satellite picture. Fish Scouter says so rather than drawing a guess; water colour and weed are better clues then.

Are there places I can't fish offshore in the Keys?

Yes. The Florida Keys National Marine Sanctuary has zones where fishing is not allowed, and some are transit only. Fish Scouter draws NOAA's no-fishing zones on the map, but always check the sanctuary's current rules before you go.

Florida Keys Offshore Fishing: Finding the Gulf Stream Edge

Offshore fishing in the Florida Keys comes down to one moving target: the edge of the Gulf Stream, which runs along the outside of the reef line and shifts closer or farther every few days. Find where the warm, blue Stream water meets the greener reef water, then fish the depth edges and humps under it: sailfish and kingfish on the 100 to 150 ft edge, wahoo down the 200 to 300 ft drop, blackfin and amberjack on the deep humps, dolphin on the edge itself.

This guide walks the Keys offshore from the reef out, explains how the Stream edge shows up on a satellite map, and shows how we plan a run with it in Fish Scouter. Whether you leave from Key Largo, Islamorada, Marathon or Key West, the structure is the same; only the distances change.

What the Gulf Stream is doing off the Keys

The current that sweeps past the Keys is the Florida Current, the start of the Gulf Stream system. NOAA describes the Gulf Stream as a warm, swift current that starts in the Gulf and flows up the East Coast before crossing the Atlantic. Off the Keys it runs west to east along the Straits of Florida, just outside the reef, before turning north up the Southeast coast.

The key word for anglers is wanders. The inside edge of the Stream can sit tight to the reef one week and well offshore the next, and eddies spin off it. Fish follow the edge because that is where warm and cool water, clear and green water, and fast and slow current meet. Bait gathers in the seam, weed piles up in the rips, and the predators patrol it.

How the edge looks on the water

Color: the water turns from green or blue-green to deep cobalt blue over a short distance.
Temperature: the console thermometer jumps a degree or more within a mile or two.
Weed lines and rips: sargassum lines up along the current seam, often with a visible tide-rip of choppy water.
Birds and flying fish: frigatebirds circling high, terns working low, flying fish breaking out ahead of the boat.

The offshore structure, from the reef out

The Keys drop from the reef into deep water quickly, which is why the offshore run is short compared with most of the US coast. Here is the order you cross it.

Zone	Rough depth	What you fish for	How
Outer reef and patch reefs	15–60 ft	Yellowtail snapper, mutton snapper, grouper	Anchor up-current, chum, float baits back
The reef edge	80–150 ft	Sailfish, kingfish, blackfin	Kite or slow-troll live ballyhoo and pilchards
The drop	200–300 ft	Wahoo, kingfish, dolphin	High-speed troll lures down the drop
Deep humps	Tops of a few hundred feet	Blackfin tuna, amberjack	Be there at first light; chum live pilchards, jig or troll feathers across the top
The Stream edge and beyond	Well past 600 ft	Dolphin (mahi), billfish	Troll the edge, weed lines and anything floating
Deep drop	1,200–1,800 ft	Swordfish (daytime)	Bait on the bottom, drifting with the current; heavy tackle

The humps

The humps are underwater mountains that rise off the deep floor. The current hits their up-current face and pushes bait up, and blackfin, amberjack and dolphin stack on them. The best-known is the Islamorada Hump. Published figures for its top disagree: George Poveromo describes it rising to within about 200 ft of the surface from 500 to 700-plus ft, while other accounts give a deeper top. Our own read of NOAA's depth grid puts the shallowest cell near 340 ft. The lesson: trust your sounder, not one number. Marathon and Key West boats fish their own humps offshore of the Middle and Lower Keys.

Saltwater Sportsman notes that the big blackfin at the Islamorada Hump are best from February through June, though blackfin are around all year. First light is the classic time to be on top of it.

Seasons offshore in the Keys

Winter (December–March): sailfish season. Cold fronts push sailfish down the reef edge; the day or two after a front, with a north or northwest wind, is the classic kite day. Kingfish on the edge too.
Spring (April–June): dolphin build along the Stream and weed lines, blackfin on the humps, the first big wahoo pushes.
Summer (July–September): dolphin and daytime swordfish. Calm seas make the long run easy, but the Stream edge can disappear on a temperature map; watch color and weed instead.
Fall (October–November): wahoo on the drop around the full moon, blackfin back on the humps, sailfish arriving with the first fronts.

Our Florida Keys water page carries the full month-by-month calendar, and the fish-by-water guides for Keys dolphin, Keys sailfish, Keys wahoo and Keys blackfin go deeper. For inshore and reef seasons, see the best time to fish the Florida Keys.

Where is the Gulf Stream today? Reading the satellite map

The fastest way to find the edge before you leave the dock is a sea surface temperature (SST) map. NASA JPL's MUR analysis, served by NOAA CoastWatch, is a daily map at about 1 km resolution built from many satellite passes, with cloud gaps filled in. That means there is a map every morning, even when it was cloudy.

The edge on an SST map is the line where the temperature changes fastest as you move offshore. Two warnings:

Gap-filled maps smooth things. Where clouds covered the water, the map is an estimate. A single satellite pass with no gap filling shows sharper breaks, but clouds leave holes.
Summer hides the edge. When the whole Straits are the same temperature, the edge simply isn't in the SST. That is when water color and weed lines matter more. We cover that in how to read water color offshore.

How we plan a Keys offshore day in Fish Scouter

We built Fish Scouter's offshore layers for exactly this run. Here is what is in the app today for the Keys and Southeast Florida:

Gulf Stream & water temp layer. Today's satellite water temperature with the Stream's edge traced through it and its temperature in the legend. When the MUR servers are down, it falls back to NOAA's mirror or NOAA STAR's blended SST, and if all of them fail it shows the last good map (up to three days old) with its date. In summer, when there is no clear edge, it tells you so instead of drawing one.
Water temp, satellite pass. What the polar satellites actually saw, without gap filling, for sharper temperature breaks.
Water colour, blue-water edge. Chlorophyll from Copernicus Sentinel-3, with the blue-water line drawn.
Weed / sargassum. A three-day satellite weed map, with the cloudy patches shown as "couldn't see" so empty water isn't mistaken for no weed.
Live current (radar). Measured surface current from shore-based HF radar, hourly. It covers Miami to Palm Beach today; the Keys radars show up when they are reporting.
Keys no-fishing zones. NOAA's sanctuary zones where fishing is not allowed, drawn on the map.
The structure itself. Thousands of mapped reefs from the state's reef tract data, NOAA-charted named reefs and shoals, the humps and deep ledges read from NOAA bathymetry, and trolling marks along the 120 ft and 250 ft edges. Marks that fall inside a closed zone are labeled as closed.

On the Guide plan, the troll plan turns that into a route: pick sailfish, kingfish, wahoo, blackfin, amberjack, dolphin or daytime swordfish, and it lays out a run from where you are to the water that fish lives on, then troll waypoints along it. For dolphin it follows today's Stream edge. Take me there then steers you to each stop with a live arrow. We walk through it in trolling the Florida Keys by species.

The troll plan draws straight lines between waypoints. It does not route around reef, shoals or closed zones, and Fish Scouter is not for navigation. Use your chart plotter and your eyes.

Rules and safety offshore

Sanctuary zones. The Florida Keys National Marine Sanctuary updated its zones under the Restoration Blueprint. Some areas are closed to fishing and some are transit only. Check the sanctuary's regulations before you fish a new spot.
State or federal water. Past the state line, federal rules apply to many species. Check FWC and NOAA Fisheries; rules change. Fish Scouter's rules card on each fish names the agency and the day it was checked.
The Stream itself. Wind against the current stacks up steep, short seas fast. A northeast or east wind against the eastbound current in the Straits is the classic bad mix. Check the seven-day outlook before you commit.

Try it on your next run

Pull up today's Gulf Stream edge, the weed and the humps on one map before you leave the dock. Try Fish Scouter free and plan your next Keys offshore day around where the water is today, not where it was last week.