Today's combined ozone and PM2.5 loop below (left) shows areas of Moderate to Unhealthy levels in Southern California and central Oregon. The Unhealthy AQI readings in central Oregon are due to high concentrations of PM2.5, which are presumably a result of the smoke from the Two Bulls wildfire burning about 10 miles from Bend, Oregon. The HMS KML image below (right) shows plumes of light to heavy smoke concentrated over this region.
More on the West Coast: high levels of ozone in Southern California are assumed to be the main cause behind elevated AQI levels, as seen in the EPA KML image below. The urban areas of Sacramento and Los Angeles are experiencing a low pressure system, resulting in close to stagnant winds with little to no mixing in the atmosphere, creating the buildup of ozone concentration.
The NAAPS model below predicts sulfates to be the cause of the moderate levels of PM2.5 the Eastern US has been experiencing for the past several days. Elevated surface concentrations of sulfate are seen all throughout Eastern US, with higher concentrations over Alabama and NE Texas.