A giant cloud of Saharan dust the size of the continental United States floating over the Atlantic Ocean was expected to spread across the Gulf Coast region this week. By the time the thick plume reaches Florida, it will have traveled over 5,000 miles from North Africa.
The National Weather Service office in Puerto Rico warned of poor air quality and advised people with respiratory issues such as asthma to wear masks.
The plume will have lost some density by the time it reaches South Florida and other Gulf Coast states by the middle of the week, but residents may still notice that the world outside appears different as dust high in the atmosphere scatters sunlight.
“Typically we have nice blue skies, but with the dust, the whole sky looks soft and warm because the particles themselves are red,” said Joseph Prospero, professor emeritus at the University of Miami Center for Aerosol Science and Technology.
“Everything looks muted,” he said.
Dust plume season is just beginning
The transport of dust from the Sahara in North Africa to far-flung places across the globe is one of the great wonders of the weather world. And we’re right at the start of the season when dust most commonly moves across the Atlantic.
The dust headed toward the United States left Africa last week and drifted into the Caribbean over the weekend.
“It’s very hazy in Puerto Rico,” Emmanuel Rodriguez, a meteorologist with the weather service, said late Sunday.
It’s the first significant plume of the year after a few smaller ones crossed the ocean in May.
“The one out in the Atlantic now is big,” Jason Dunion, a meteorologist who monitors hurricanes and Saharan dust, said Friday. “It’s the biggest one we’ve had so far this season.”
The plume was stretched across the central Atlantic on Friday and started filtering into the Caribbean over the weekend.
Dunion said he had been in Puerto Rico amid a Saharan dust outbreak.
“There’s a lot of dry air, and you don’t feel that dry air, but the clouds feel it because as they grow and form thunderstorms, they run into that dry air, and they just collapse,” he said. “They get stifled. So as this comes through to a place like Puerto Rico, you’re going to tend to have fewer thunderstorms. It’s going to probably be one of our hotter days. And very hazy. The haze is incredible.”
If a few stray showers fall through the dust layer, he said, it looks like dirt has coated your car. “It’s probably traveled about 3,000 miles; it gets washed out into your car,” he said.
After overtaking the Caribbean, the dust is expected to push into the Gulf of Mexico and then into the nearby states, from Florida to Texas, with hazy skies expected in the region potentially through Friday.
Winds scoop dust up from the Sahara
The process that drops dust on a car in San Juan begins in the vast expanse of the Sahara. It also involves the Sahel, a narrow strip of moister, cooler land just below it.
The temperature difference between the two regions helps create “tropical waves,” areas of low pressure with embedded thunderstorms that move across the Sahel and send out powerful winds that rush into the Sahara. The tropical waves are the same phenomenon that can grow into powerful hurricanes at this time of year.
The winds lift the dust from the Sahara up into the atmosphere, creating a dry layer of air that hovers about a mile above Earth’s surface and can be up to 2.5 miles deep; scientists call it the Saharan Air Layer.
Sometimes simply the heating of the Sahara and the hot rising air create winds that can lift dust particles off the ground, but “the biggest dust outbreaks each summer have tropical waves in the mix,” Dunion said.
The dust sporadically drifts into the Middle East and sometimes north into Europe, where it can turn the skies orange.
More commonly, the dust is whisked across the Atlantic Ocean by a conveyor belt of winds known as the African Easterly Jet, flowing from east to west. The dust travels to South America and the Caribbean and sometimes, like this week, as far as Florida, Alabama, Mississippi, Louisiana and east Texas.
Meteorologists have plenty of notice when one is headed their way. The dust storms are visible by satellite developing over the Sahara seven to 10 days before they reach the Caribbean or the Gulf of Mexico, Dunion said.
He has flown into the dust layer and described it as similar to a “London fog” that has a “brilliant orange glow” at sunset.
The thickest plumes can cause air quality issues, irritating respiratory systems and exacerbating allergies. They can act as a cap and trap heat near the ground, or they can have a cooling effect, blocking the sun’s radiation.
The dust events happen year-round, but the largest occur from mid-June to late July. After early August, the dust plumes do not tend to travel as far west over the Atlantic.
“It happens every year; some years have more dust transportation across the Atlantic than others,” said Sammy Hadi, a meteorologist at the National Weather Service office in Miami. “It’s like rinse and repeat every year; it’s part of a normal cycle of Earth’s oscillations.”
This dust storm brings good news to those closely watching the Atlantic hurricane season, which officially began Sunday: The dry air and strong winds that accompany a dust storm suppress the development of tropical storms, which need moisture to grow. There’s an ongoing battle between storms trying to form and the dust layer overpowering them.
“Mother Nature is fascinating,” Dunion said. “It set up this Saharan dust factory right next to the hurricane nursery.”
This article originally appeared in The New York Times. © 2025 The New York Times
