This was not your usual dust storm that kicks up in the late afternoon. It was just before 9:30 a.m. Monday that we spotted the dust.
A lot of people thought it was smog, but it kept growing and rolling north over the valley.
Just how dusty was it?
Take a look at our tower camera video from the top of South Mountain. We've sped up the video -- creating a timelapse for you to show the dust as it moved through the valley.
You should be able to see downtown and Camelback Mountain, but the dust made that impossible.
"I turned around and I see a big old wall and it's cutting the city in half and then I go a couple of feet up and I turn around again and the whole city's covered in the dust," says Jonathan Perez, who went hiking on Piestewa Peak.
Closer to the ground, an Arizona Department of Transportation camera showed how it looked around 10:15 a.m. Monday on State Route 51 near the Glendale exit.
Another shot from that same camera about 12 minutes later shows how it's supposed to look when it's "not" dusty.
And a little bit north of there, another ADOT camera showed the blowing dust with the mountains in the background at SR 51 and Thunderbird.
With the higher winds came a drop in temperature -- that no one was complaining about, especially other hikers we talked to.
"The good thing is it cools it down for the hike. As long as you aren't wearing contacts I think you can manage pretty well!" says hiker Jennifer Clack.
It took about 3 hours for the dust to move through.