The haze over Phoenix is windblown dust, not smoke from California wildfires. What to know

As hazy skies linger over metro Phoenix, some people may wonder if smoke from the Southern California wildfires is to blame. But while the Valley is under the influence of a similar weather system, it’s actually dust clogging up the air.

The worst Santa Ana winds in over a decade have hit Los Angeles and Ventura counties, rapidly spreading fires across the dry landscape that hasn’t seen substantial precipitation in months. The same winds are blowing the smoke out to sea rather than into Arizona.

Gusts of up to 80 mph on Tuesday and Wednesday rapidly escalated three brush fires in the area: the Palisades Fire, the Eaton Fire in the San Gabriel Valley, and the Hurst Fire in the northern San Fernando Valley. With thousands of acres burning, L.A. has been overrun with smoke.

Given the proximity to L.A., Phoenix residents may be concerned wildfire smoke will spread to Arizona. But with the east-to-west wind flow related to the Santa Ana winds, what we’re seeing is dust particles rather than smoke.

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“Those fires are blowing out towards the ocean and the smoke is going out into the Pacific,” said Will Humble, the executive director for the Arizona Public Health Association. “But that same weather system is causing winds here, so it’s kicking up desert dust.”

Dust is worsening the Phoenix air quality

Fine particulate pollution increased to moderately unhealthy levels Wednesday morning as gusts blew dust across the Valley.

Humble attributes the dust to winds related to the low-pressure system lingering over the Southwest that ultimately contributed to the Santa Ana winds in California.

Wind is both good and bad for fine particulate matter pollution, also known as PM2.5 and PM10 depending on the size of the particle. PM2.5 includes particles less than 2.5 micrometers in diameter and PM10 particles are less than 10 micrometers in diameter.

Stronger winds can clear the air and disperse PM2.5 pollution like diesel exhaust, chimney smoke, fireworks and other pollutants.

“The wind has been a good thing, even though it’s kicking up some desert dust,” Humble said, “It gets rid of the combustion and other stuff we have by having 4.5 million people living here.”

But it’s been so windy, that desert dust is blowing around, causing a moderate spike in PM10 particles. Wind speeds around 10 miles per hour are ideal for dispelling pollution, but anything over 20 miles per hour will likely stir up dust.

And with minimal rain since Aug. 22 in Phoenix, conditions on the ground are increasingly dry, making it easier for winds to unsettle dust.

“We’ve also had a really dry 2024 going into 2025 here in Arizona. That has made things worse in regards to blowing dust,” said Brody Droppleman, an air quality meteorologist for the Arizona Department of Environmental Quality.

Dust pollution is slightly less dangerous than smoke

While all air pollution can endanger people’s health, dust pollution is the lesser of the two evils according to Humble.

“Dust is often less dangerous than combustion sources, but still harmful to the lungs,” he said.

Still at risk are people with underlying health conditions like chronic obstructive pulmonary disease (COPD), emphysema and asthma in both adults and children.

Dust particles smaller than 10 micrometers in diameter can enter the lungs and possibly the bloodstream, leading to health problems.

Compared to Phoenix air quality around the holidays and after New Year’s, things are definitely improving.

“Our particulate levels are elevated a little bit, but they’re much better than the day after New Year’s when everyone was lighting off fireworks,” Humble said. “It was off the scale, toxic almost.”

Will wildfire smoke disperse to Arizona this week?

As winds continue to push west, most of the wildfire smoke will continue blowing into the Pacific rather than heading east toward the surrounding region.

“The good news for Arizonans is all that smoke from the L.A. wildfires has stayed away out west,” Droppleman said. “We do not expect that smoke to come over to Arizona for at least a couple more days.”

If the wind changes directions and smoke heads east, Droppleman expects minimal impacts on Arizona air quality. He predicts air quality issues in Phoenix overall will start to die down in the later part of the week.

While there may be a slight reprieve in the Santa Ana winds this week that could cause smoke to disseminate, it likely won’t last long.

“The forecast shows the winds will slow down a bit where smoke could make a little headway, but by Friday, those Santa Ana winds are coming back again,” Humble said. “It’s awful.”

Hayleigh Evans writes about extreme weather and related topics for The Arizona Republic and azcentral.com. Email her with story tips at hayleigh.evans@arizonarepublic.com.

This article originally appeared on Arizona Republic: Windblown dust, not wildfire smoke is worsening Phoenix air quality

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