A dangerous fungal storm could engulf parts of Arizona within hours, blasting roughly 1.5 million people with thick dust and potentially harmful spores.
The National Weather Service issued a blowing dust advisory Wednesday for large sections of central and southern Arizona, where wind gusts could reach 55 mph.
Phoenix, Tucson, and Phoenix-area communities, including Buckeye, Avondale, Ahwatukee, and Queen Creek, are among the cities in the storm’s path. The advisory covers portions of Maricopa, Pinal, Pima and Santa Cruz counties.
The worst conditions are expected between 3 p.m. and 10 p.m. local time, or 6 p.m. Wednesday to 1 a.m. Thursday ET.
Visibility could fall to just one-quarter of a mile, making travel hazardous well into the night. Drivers caught in the swirling dust could lose sight of the road within seconds.
“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. Turn the lights all the way off and keep [your] foot off the brake pedal. Remember, ‘Pull Aside, Stay Alive,’” the NWS advised in their alert.
The dust could bring another, less visible threat.
Coccidioides, a microscopic fungus found in Arizona soil, can be thrown into the air during dust storms. Inhaling the spores can cause Valley fever, a lung infection that can turn deadly in severe cases.
Arizona officials have not confirmed that the approaching storm will contain the fungus. The Centers for Disease Control and Prevention, however, says Coccidioides is found throughout Arizona and neighboring Southwestern states.
“Persons with respiratory problems should make preparations to stay indoors until the storm passes. Be ready for a sudden drop in visibility to near zero,” the NWS warned in a statement.
People with asthma, heart disease and other chronic respiratory conditions face some of the greatest risks from the fungal storm, according to forecasters.
“Those most at risk may feel better if they avoid outside exercise today, keeping windows and doors closed to help reduce exposure,” the weather agency added.
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For most people who inhale the spores, the immune system fights off the fungus or the infection causes mild, flu-like symptoms such as fever, coughing and headaches.
Severe infections can spread to the bones and organs and become fatal.
The CDC estimates that breathing in Coccidioides causes between 15% and 30% of pneumonia cases in the Phoenix and Tucson areas.
Forecasters also warned that Arizona’s severe thunderstorms and powerful winds could produce haboobs, enormous walls of dust swept up from bone-dry ground.
Extreme heat, drought, and monsoon winds can fuel more frequent and intense dust storms that can carry Coccidioides spores.
The fungal storm threat comes as the same areas of central and southern Arizona remain under an extreme heat warning through Friday.
The heat index could approach 110 degrees, compounding breathing problems for anyone caught outside.
The heat index is the “feels like” temperature, which climbs when humidity makes the air feel hotter. On a 90-degree day, high humidity can push the “feels like” temperature to 105 degrees.
“Overexposure can cause heat cramps and heat exhaustion to develop and, without intervention, can lead to heat stroke,” NWS said.
A massive heat dome blanketing the western half of the U.S. is fueling the punishing forecast. The high-pressure system traps heat and humidity close to the ground like a lid on a boiling pot, leaving Arizona to face extreme temperatures, violent winds and clouds of potentially dangerous dust.
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