TEMPE, AZ (AZFamily) — The dust storm that hit the Valley Monday night has been rated a Category 5 on the PHX Dust Storm Scale, the highest level, and unhealthy air remained over Phoenix into Tuesday evening.
The PHX Dust Storm Scale was created by an ASU-led team to measure the severity of dust storms in the Valley. Category 5 events are rare.
What a Category 5 means
Dr. Ryan Heintzman, a professor at ASU’s School of Geographical Sciences and Urban Planning, helped create the scale.
“In the 15 years that we’ve been looking at these dust events, this is only the fifth time that we’ve seen a Category 5 storm,” Dr. Heintzman said.
Heintzman said the scale originally developed as a way to identify high exposure to dust and particulate matter. Ratings run from one to five, based on how much dust is packed into the air. The particles are roughly five times narrower than a strand of human hair.
“If you’re outside for an hour during a Category 1 event, it might be something like 250,000 pieces of dust that you’re inhaling,” Heintzman said. “A Category 5 is five times that amount. If you’re outside during a Category 5 event, it would be something like over a million pieces of dust that you would be inhaling.”
Arizona State University created a dust storm rankings system measuring the dust concentration.(Arizona State University)
Health concerns
Dr. Frank LoVecchio, an ASU professor and emergency room physician, said certain groups face greater risk during events like this.
“I would say if you have lung disease, heart disease, the very young, the very old, if for some reason you’re immunosuppressed, those are people who get into trouble during this time,” LoVecchio said.
Tracking the storm in your neighborhood
ASU has built a new dust storm dashboard that shows the storm’s category and how strongly it hit specific locations across the Valley.
See a spelling or grammatical error in our story? Please click here to report it.
Do you have a photo or video of a breaking news story? Send it to us here with a brief description.
Copyright 2026 KTVK/KPHO. All rights reserved.
