Ocean Temperature Map

An ocean temperature map shows you something no weather forecast will: the shape of the water itself. Fish do not spread out evenly across the sea. They follow temperature, and they gather where warm and cold water meet. A good SST map puts those meeting lines on a screen before you burn the fuel to go looking for them.

How to read a sea temperature map

Every pixel on the map is the temperature of the top layer of the sea. Warm water shows in reds and oranges, cooler water in greens and blues. The absolute number matters less than most people expect. What you are really reading is structure: where the colors change, how sharply, and what shape the change makes.

• Breaks. A tight band where the color flips quickly is a temperature break, often a few degrees in a mile or two. The tighter the band, the stronger the edge. Breaks are the single most useful thing on the map.
• Walls and ribbons. A long, steady line of warm water against cool water is usually the edge of a major current. The north wall of the Gulf Stream is the classic example.
• Rings. A round patch of warm water sitting in cooler water, or cool water in warm, is usually an eddy that has broken away from a current. Its whole outer edge is a break.
• Tongues and filaments. A finger of warm water pushing into cooler water, or the reverse, is a current intruding onto the shelf. The tip and the sides are worth a look.

If you want the science behind the colors, including how satellites measure the sea surface, our guide to sea surface temperature covers it in depth.

Why temperature breaks hold fish

A break is rarely just a change in temperature. It is the surface sign of two water masses meeting, and that meeting does real work. Nutrients get pushed up, plankton grows, and baitfish come to feed on it. Predators follow the bait. Current along the edge also concentrates weed, debris and anything drifting, which is why a weed line on a temperature break is such a good sign.

Species have preferred temperature ranges, and they tend to hold along the edge of that range rather than in the middle of it. Our guide to tuna fishing and water temperature goes through the ranges species by species. In practice the move is the same for most offshore fishing: find a break near your target temperature, then fish the edge.

Using the map before a trip

Start wide, then work in. A sensible order:

• Pan out far enough to see the big features: the main current, any eddies, and the general split between warm and cool water off your coast.
• Zoom toward your range. Colors on this map rescale to the water in view, so breaks that were invisible at ocean scale will sharpen as you zoom in.
• Mark the breaks within reach, and note which side is warm and which is cool.
• Check the depth under each one. A break sitting over a canyon edge or a steep drop is usually worth more than the same break over flat bottom.
• Remember the map is a recent snapshot. Eddies drift and breaks shift from day to day, so expect a feature to have moved a little by the time you get there.
• Finally, check the ride. A great break is no use if the boating forecast says the run out there is a bad idea for your boat.

Temperature and currents work as a pair. Our live ocean current map shows which way the water is moving, which tells you where today's breaks are likely to be heading.

Waters the temperature map covers

The live temperature layer is rendered for a defined set of fishing and cruising grounds. Pan to any of these and you will find it:

• The US East Coast, the Gulf Stream and the Caribbean
• The Gulf of Mexico
• The US West Coast
• The Great Lakes
• Mexico's Pacific coast and the water offshore of it
• Central America
• Brazil, both the northeast and the south and southeast
• The Mediterranean
• The northern Arabian Sea
• Australia: the north, northwest, west coast, south, southeast and Tasmania, and the east coast and Coral Sea
• New Zealand, including the Chatham Islands

On the Great Lakes the map shows lake surface temperature, which matters just as much for finding fish in fresh water as it does offshore.

Common questions