Average Ocean Temperatures for Oregon
You'd expect sea temperatures to grow cooler as you head north along Oregon's shore. But that is true only in winter and spring. From May to November, the southernmost site measured, Port Orford, has the coldest water.
Local conditions create the strange pattern. Inlets, bays and rivers influence the ocean's temperature along Oregon.
The water temperature at Port Orford is measured in the open sea. But to the north, temperatures are taken in inlets where the sheltered water gains a little warmth. The ocean at Charleston, near Coos Bay is monitored in a bay near the entrance to an inlet. The water at Newport is measured in Yaquina Bay, east of highway 101, near the Hatfield Marine Science Center.
Seaside in northern Oregon has the warmest ocean of all the places measured on the Oregon coast during summer, despite temperature readings taken there in exposed water. The unusually high temperature is due to the influence of the Columbia River, which empties into the ocean a short distance to the north.
Just around the corner, along the river mouth at Astoria, the water in summer gets even warmer. The river temperature near Astoria peaks at 68 °F (20 °C) in early August, many degrees higher than the ocean.
Only the hardiest will want to stick more than their bare toe in the ocean off any Pacific beach in Oregon. The water throughout the year stays too cold for swimming without a wetsuit.
These coastal water temperatures are averages compiled by the National Oceanographic Data Center. Actual ocean temperatures do vary from year to year depending upon the weather and the flow of ocean currents.