A Cloudy Cloak Over the Northwest

In mid-September 2026, cool marine air from the Pacific created morning clouds over western Washington and Oregon. Low clouds and fog reached inland as far as the western foothills of the Cascade Range. Near the shore, higher parts of the Olympic Mountains and the Oregon Coast Range stood above the clouds like islands.

NASA’s Terra satellite recorded this cloud cover on September 19, 2026. An instrument called MODIS captured the scene at about 10:45 a.m. Pacific Time. Clouds were also widespread over the ocean, and smoke from wildfires occupied valleys in the North Cascades.

The National Weather Service reported that marine air had moved inland for several nights. This air carried marine stratus, a form of low cloud. These clouds develop when moist air close to the ground is trapped under a warmer layer called a temperature inversion and then cools until water vapor condenses. Early on September 19, the cool, moist air was especially strong, so the clouds reached the Cascade foothills. In some locations, the layer reached the surface and produced fog.

That afternoon, NASA’s Aqua satellite observed the region at about 4:15 p.m. Pacific Time. Skies had already cleared across much of the area, but a few marine clouds remained along the Oregon coast, where temperatures stayed lower than farther inland.

Why did the clouds cover so much of western Washington and Oregon in the morning, but clear in many places by the afternoon?