Why so red? It's a byproduct of the massive wildfires that recently burned a large area in Siberia.
The atmospheric winds are aligned this week to carry the smoke across the Pacific Ocean and into the Pacific Northwest.
First up, to get an idea of just how much smoke is in the atmosphere, look at this visible satellite image taken on April 14 of the southeastern Siberia area where the wildfires got out of control:
Credit: NASA image courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC. Caption by Adam Voiland.
Where did the smoke go? This graphic is a model trajectory tracing back the air pattern across the Pacific Ocean over the past week. Note the air from the wildfires makes somewhat of a bee line toward Seattle (with a brief stop for a loop-de-loop in the central Pacific:)
Amazingly the smoke is still quite intense when it gets here -- check out this high-resolution satellite image from Saturday and note the haze over Washington and British Columbia: