Which kind of weather usually forms over the northwest united states in the summer because of maritime polar air masses?

Cloudy and damp weather

Explanation:

Maritime Polar can form anytime of the year and because they are not as cold as continental polar which brings hot and humid air

The cool and moist Maritime Polar air masses brings cloudy and damp weather to the USA.

Maritime polar air masses form over the northern Atlantic and the northern Pacific oceans. They most often influence the Pacific Northwest and the Northeast.