Dust in the wind

While walking to the car I looked at the light poles and the light was shimmery and strange, the air a bit heavy and the cars in the distance were not clearly visible. The mysterious air condition remained unsolved until the next morning. Once again, the light was somewhat different, no clear skies (which I've for 99% of the time so far), and visibility was not more than a couple kilometers (even the big buildings were behind this changed air layer). I know this from back home with fog, but then, humidity is like maximum 20 % here...
Well, it turns out it was dust in the air, blown into the city from the desert :)