@gkiritz
You compare satellite PM 2.5 measurements (at a very low resolution) with air quality stations data located in a valley surrounded by mountains. The satellite cannot " see " a very local concentration of pollution.
You better rely on the 2 Air quality stations shown by Windy in Leavenworth (need to zoom in).

CE959C72-67A2-423A-8965-F09349E63FEA.jpeg

And see the small i at bottom right corner of your screen or About this data in the mobile app to get more information on this layer, where it is said that " Due to the horizontal resolution of the systems used by CAMS, it is not possible to represent local effects due to the immediate vicinity of sources (high-traffic road, industrial plant...) ".