Recently, there was a major front that passed over. Fronts are like air vacuums, cleaning the air. This happens because the dust in the air either forms cloud droplets or are absorbed by cloud droplets, the front then moves away with the dust or sends it back to the ground by rain. This is what happened, and the air is very clean. How can you tell? Usually there is an aureole around the sun by larger particles scattering light forward. It is typically a couple degrees wide, but if there is little or no aureole it means the air is really clean. In places in Antarctica or up above cirrus clouds, the effect is very striking.