Science

Why a Saharan Dust Storm Is Heading for the United States

A boat speeds across a bay in front of a shoreline enveloped in a haze. The air is gray, and the mountains and buildings are barely visible.
A dust cloud from the Sahara sits over the city of San Juan, Puerto Rico, on Monday. Ricardo Arduengo/Getty Images

In what appears to be the latest biblical plague of 2020, a nearly 4,000-mile-long dust storm from the Sahara Desert is currently headed toward the southeastern coast of the United States.

This dust plume, known as the Saharan Air Layer, is a phenomenon that develops every year off the coast of Africa, where powerful winds from thunderstorms over the Sahel can push the dust many thousands of feet up into the atmosphere. A few times a year, that layer of dust sends out vast clouds that then drift over the sea.

But this year, the dust clouds that normally do little more than amplify sunsets have drifted far lower to coat Caribbean islands with a thin layer of dust and choke the air with a dry haze that in some places cut visibility by more than half. The cloud is forecast to sweep across the southeastern United States—Texas and Louisiana in particular—on Wednesday, Thursday, and Friday. Another wave of dust is expected to follow.

According to the New York Times, in those areas affected by the dust, some people with asthma and underlying lung conditions might be at risk for irritation and discomfort. Those residents should avoid outdoor activities and monitor the air quality.

One good quality of these plumes is that they typically squash any early hurricane formations with their dry air. But according to the Washington Post, the dust can also deposit enough iron into the Gulf of Mexico to spur dangerous and noxious algal blooms. It’s also possible some of the microbes and nutrients carried in the dust play an important role in local ecosystems.

For more of Slate’s news coverage, subscribe to What Next on Apple Podcasts or listen below.