A hazardous dust storm is projected to move across parts of Arizona on Tuesday, carrying the potential to distribute fungal spores linked to Valley fever. The National Weather Service issued a blowing dust advisory for southeastern Arizona from 2 p.m. to 8 p.m. local time, cautioning that thunderstorms could rapidly decrease visibility to near zero.
Residents with respiratory conditions have been advised to stay indoors, and drivers are instructed to pull over if they encounter a dust wall. This alert comes as experts warn that such "fungal storms" could affect communities in at least 11 states throughout the summer.
Dust storms can disturb soil containing Coccidioides, a fungus that causes the potentially fatal lung infection Valley fever. While Arizona officials have not confirmed the presence of the fungus in Tuesday's storm, it is developing in a region where Coccidioides is endemic. Experts anticipate the risk to increase as the Southwest enters the North American monsoon season, a period characterized by thunderstorms and strong winds that can whip up large amounts of desert soil.
Most individuals infected with Valley fever experience flu-like symptoms. However, in severe instances, the fungus can spread from the lungs to other parts of the body, including the bones and brain, which can be life-threatening.
The NWS indicated that visibility could drop to between a quarter-mile and one mile shortly after the storm's development after 2 p.m., with wind gusts expected to surpass 40 mph, and some local meteorologists forecasting gusts up to 60 mph. "If you encounter blowing dust or blowing sand on the roadway or see it approaching, pull off the road as far as possible and put your vehicle in park," the agency advised. "Turn the lights all the way off and keep your foot off the brake pedal. Remember, 'Pull Aside, Stay.'"
The advisory encompasses a significant area of southeastern Arizona, including eastern Cochise County, the Upper Gila and San Pedro River valleys, and several mountain ranges. A substantial dust storm also affected the area outside Phoenix on Monday evening, extending its reach to Tucson, over 100 miles to the south. Air quality readings in the Phoenix area on Tuesday morning ranged from unhealthy to hazardous.
Coccidioides naturally occurs in dry, sandy soils within arid regions of the U.S. Southwest. It thrives in alkaline soils with hot summers, mild winters, and low rainfall. The fungus is typically harmless unless its spores become airborne and are inhaled. The Centers for Disease Control and Prevention (CDC) notes that while these infections are considered rare, outbreaks have occurred in unexpected locations.
Cases of Valley fever have been on the rise across Arizona. Maricopa County reported 4,498 infections in the first six months of 2026 alone. Statewide, more than 12,000 cases were reported last year, with Arizona accounting for approximately two-thirds of all U.S. infections. Researchers have observed a dramatic increase in Valley fever cases throughout the Southwest in recent years. In 2024, infections surged by 42% in the Phoenix area, reaching 12,522 cases from 8,841 the previous year. Nationwide, the annual case count increased from 16,746 to 22,244.