Reading SST Charts for Pacific NW Tuna


Everyone gets enamored with early season warm water, even some people that have been fishing tuna for years. There are a couple pitfalls that need to be avoided when reading a Sea Surface Temperature (SST) chart.

The first thing you have to remember is that warm water doesn’t mean anything if it isn’t connected to the main mass of warm water coming from the south.

The water has to be fully connected so that the tuna have a clear path to our coast. A lot of times, folks get confused by looking at all the warm water dumping out of the Columbia River and that’s all it is.

Take a look at this Ripcharts ( SST chart. There is a fair amount of warm water coming out of the Columbia River and mixing with the Pacific Ocean. This shot shows that water as a warm 60 degrees, and this is not tuna water (bad news). The good news is that there is fairly consistent 56/57-degree water connected to the Washington Coast. Sometimes we experience what I call the ‘Convection Effect’, i.e. it is almost as if someone took the eastern Pacific Ocean and put it in a microwave. The 56/57-degree water can quickly be turned into 59/60-degree tuna water with the right combination of wind and current.


When the tuna show up, it is typically (there are always exceptions) all about SST and not chlorophyll (a measure of the amount of plankton in the water). The chlorophyll tends to come naturally, but the warm 59-degree water is what we look for.

CAVEAT: In early 2010, I was fishing 56/57-degree water that was full of tuna. In the late season, fishing colder water is more common.


It’s all about the chlorophyll and even then….a lot of times, they are in the green/cold water. READ THE LIFE! Don’t pass a bunch of birds that are going nuts and partaking in a feeding frenzy, even if the water is cold and green!


People can also get misinformation when reading SST charts. To get an accurate look at the true water temps, you have to use a satellite shot that was taken early in the morning between 1AM and 6AM, before solar heating has taken affect. Also, use the GRANULE (single) shots, not the daily or composite shots. The latter shots are inaccurate. The Ripcharts SST chart above is a great chart for getting a sense of what is happening on a large scale, but I would not use it to plan a day’s trip because the shot was taken at 4:08PM.


RIPCHARTS does a great job at providing a friendly user interface with great data. Contact the fine folks at Defiance Marine or feel free to send me a message on We will help you dissect and analyze your SST and Chlorophyll data.

No one can predict when exactly the tuna will show, but I am willing to bet that tuna will be hitting the docks of Westport within a month!

Stay TUNA’D and I look forward to seeing you all in Westport this summer!

Capt. Tommy Donlin, the BD Outdoors Pro Staff representative for the Pacific Northwest, has more than 20 years of experience fishing the waters from Sitka, Alaska, to Clarion Island off the coast of Mexico. He chases everything that swims off the Washington coast, including tuna, salmon, lingcod, ha...