We're having bad Santa Ana conditions right now which are adding fuel to that big fire burning east of L.A. near Cabazon. Hot, dry winds breezing through the canyons and passes also tend to keep the smog that would in large part normally drift north & east of here trapped in the basin, contributing to the visible smog (particulate matter) you might be seeing. Certainly the ash & smoke from the fire may be a contributing factor today, too.