The Brief Dust storms striking the Phoenix area reached Category 5 levels based on weight, wind speed, duration, and particulate matter. Dust has been clinging to the air across Phoenix following strong dust storms in the last week, leading to poor air quality and the potential for more monsoon storms in the coming days. What we know:While conditions cleared up temporarily, meteorologists report that dust storms tend to pop up in the late evening. Both dust storms on Aug. 3 and Aug. 6 were Category 5. "For someone with severe asthma or COPD, a dust storm can turn a normal day into an emergency room visit."