A dust storm in the Valley hit Monday night and reached Category 5 on the PHX Dust Storm Scale, the highest rating on the system. Dust Storms In Phoenix stayed tied to unhealthy air over Phoenix into Tuesday evening, keeping the event active beyond the first blast.
Dr. Ryan Heintzman, an ASU professor at ASU’s School of Geographical Sciences and Urban Planning, said this was only the fifth Category 5 storm seen in 15 years of looking at dust events. He and other ASU researchers created the scale to measure dust storm severity in the Valley, and the new dashboard shows both the category and how strongly a storm hit specific locations across the Valley.
PHX Dust Storm Scale
The scale runs from one to five based on how much dust is packed into the air. Heintzman said a Category 1 event can mean about 250,000 pieces of dust inhaled during an hour outside, while a Category 5 event can mean over a million pieces of dust inhaled during that same hour.
That gives readers a simple read on why the Monday night storm drew attention. Category 5 is not just the top line on a chart; it sits at the far end of a scale built to capture exposure during dust events, and the number of Category 5 storms has been limited over 15 years of tracking.
Frank LoVecchio
Dr. Frank LoVecchio, an ASU professor and emergency room physician, said people with lung disease, heart disease, the very young, the very old, and people who are immunosuppressed can get into trouble during dust events. For people in those groups, the practical step is to treat lingering unhealthy air as part of the event, not as a separate afterthought.
Heintzman’s scale helps explain the severity, but it does not replace the health warning that came with the storm. The dust rating showed the exposure level was extreme, and the air over Phoenix still had not cleared by Tuesday evening.
Phoenix Tuesday evening
For anyone in Phoenix, the immediate takeaway was simple: Monday night’s storm was not just dusty, it was a top-end event that continued to leave unhealthy air in place into the next day. People at higher risk, as LoVecchio described them, had the strongest reason to limit exposure while the air remained poor.
