Are fungal storms becoming more common? What they are, when they strike

• Extreme weather events like dust storms, floods, and high winds are spreading dangerous fungal spores.
• Climate change is causing fungi to become more resilient and expand into new geographic areas.
• While most common in the Southwest, fungal infections like Valley Fever are now appearing in other states.
• Only a small fraction of fungi are harmful to humans, with the greatest risk to those with weakened immune systems.

Fungi are taking the U.S. by storm — and not in the good way.

What’s being described as “fungal storms” isn’t a new kind of weather, experts say, but a dangerous mix of conditions where airborne spores hitch a ride on dust, winds and flooding.

Fungi aren’t literally storming areas like rain or hail, but storms act as the vehicle while the spores supply the threat.

As climate change drives hotter, drier, and more extreme weather, these microscopic threats are spreading farther and becoming more resilient — sometimes with deadly consequences.

How fungus storms form and spread

Fungal spores can spread anytime soil is disturbed and particles are sent into the air. Dust storms are the most visible driver, especially in the Southwest. BBC Science Focus Magazine reported that strong winds can lift dry, contaminated soil into the atmosphere, sometimes forming fast-moving walls of dust known as haboobs. These clouds can sweep particles — including fungal spores — across large distances, increasing the risk of inhalation.

“Sand and dust storms do not just mean dirty windows and hazy skies," Secretary General of the World Meteorological Organization Celeste Saulo told the magazine. "They harm the health and quality of life of millions of people and cost many millions of dollars through disruption to air and ground transport, on agriculture and on solar energy production.”

Other triggers include heavy rain, flooding, and mud that dries afterward. Hurricane Hilary in 2023, for example, prompted doctors in the Desert Southwest to monitor for Valley Fever, a fungal infection linked to soil-borne spores, Fox Weather reported during the recovery efforts in August 2023. Winds from monsoons, tropical storms, and even seismic activity can lift spores, while consistent rain and atmospheric rivers create the moist conditions that allow fungi to thrive. This sets up a repeating cycle: wet conditions multiply spores, and the next round of high winds spreads them farther, increasing exposure risk.

"I’m not sure we can prevent people from getting valley fever,” Christie Michie, assistant director of public health in California's Monterey County, told USA TODAY during a September 2025 outbreak. “It’s very difficult to avoid dust in our environment. But what we don’t want is people get really sick with valley fever.” Her community, a cool coastal agricultural region, had just a couple of dozen cases a year in past decades but now averages hundreds.

But weather isn't the only trigger. Construction, agriculture and wildfires can also disturb soil and release fungal particles into the air. Once airborne, these microscopic spores are easily inhaled without people realizing it.

At the same time that opportunities for spores to spread are increasing, the fungi themselves are becoming more resilient, Earth.com reported. Species like Aspergillus thrive in warmer temperatures and changing environmental conditions, and widespread use of azole compounds in agriculture and medicine is driving drug resistance. This allows some fungi to survive longer and spread more easily, raising the risk of severe infections.

Where fungal storms are are most common

Fungal infections tied to airborne spores remain most common in the Southwest, particularly in dry regions of Arizona, California, New Mexico and Texas where these organisms naturally live in the soil, according to BBC.

In the U.S., illnesses linked to these fungi — most notably Valley Fever — are still concentrated in that region, making it the primary hotspot for exposure.

But that footprint is expanding. Cases are increasingly being identified outside the Southwest, including in states like Oregon and Washington, suggesting the geographic range is shifting.

According to Earth.com, species like Aspergillus are moving into areas that were previously inhospitable as warmer temperatures and changing moisture patterns reshape where they can survive.

"We’ve already seen the emergence of the fungus Candida auris due to rising temperatures, but, until now, we had little information on how other fungi might respond to this change in the environment," Dr. Norman van Rhijn, at the University of Manchest, told Earth.com

The result is a widening risk zone: while the Southwest remains ground zero, experts warn exposure could spread farther into the Midwest and even parts of Canada in the coming decades.

What are the most common fungal species?

Several fungal species are most often carried by dust and other soil disturbances, posing health risks when inhaled. The key players include:

• Coccidioides species – Responsible for Valley Fever, found mainly in the dry soils of the U.S. Southwest. Spores become airborne when soil is disturbed by dust storms, construction, or earthquakes.
• Aspergillus species – Includes A. fumigatus and A. flavus, which thrive in warm, humid soils and decaying vegetation. Airborne spores can travel long distances and infect lungs, especially in immunocompromised individuals.
• Histoplasma capsulatum – Common in soils enriched with bird or bat droppings. Disturbances such as construction or flooding can send spores into the air.
• Blastomyces dermatitidis – Found in moist soils and near water bodies; spores can spread when soil is churned by storms, floods, or human activity.

Of these, Coccidioides and Aspergillus are generally the most dangerous to humans. Coccidioides can cause severe pulmonary disease and chronic infections in some cases, while Aspergillus species, especially drug-resistant strains, can lead to life-threatening infections in people with weakened immune systems.

Are all fungi dangerous or deadly?

Most fungi are harmless. In fact, many are beneficial, helping decompose organic matter, recycle nutrients, or even make food like mushrooms, bread and cheese. Only a small fraction of species can make humans sick, and serious infections are usually limited to people with weakened immune systems.

The fungi that pose the greatest threat during so-called “fungal storms” are soil-borne or airborne pathogens. While these species are dangerous, they represent a tiny fraction of the fungal world.

Brandi D. Addison covers weather across the United States as the Weather Connect Reporter for the USA TODAY Network. She can be reached at [email protected]. Find her on Facebook here.