GRAND MARAIS – Ice anglers and snowmobilers near the Boundary Waters were among those who noticed brown spots on their vehicles and other gear left outside Saturday, March 15.

The spots didn’t come from the usual mud-slinging that accompanies the spring thaw. Rather, it came from something known as “dirty rain.”

Paddle and Portage spoke with Jonathan Wolfe, meteorologist at the National Weather Service in Duluth, who said the dust or dirt that fell from the sky was the result of dust being blown in from the Southwest and Southern plains, which was then “brought down with falling precipitation.” Most of the dust, or small particles of dirt, came from New Mexico, Texas, Oklahoma, or Colorado, according to Wolfe.

“It’s fairly common for this to happen,” said Wolfe. “Sometimes it’s just more pronounced.”

Canoes at Rockwood Lodge after a rain event March 15. Photo by Mike Seim

Wind gusts over 80 mph were reported in Colorado and parts of Texas Friday, March 14. Winds of that magnitude kick dust into the atmosphere where it is later deposited via rain or snow, Wolfe explained.

While the phenomenon is somewhat common, its severity depends on the amount of dust present in the atmosphere, Wolf said. In extreme cases, “dirty rain” can reduce air quality and visibility, creating additional hazards for motorists and those with respiratory conditions, according to the National Weather Service.

Support this type of storytelling from the Boundary Waters region by becoming a member of P&P or making a one-time contribution.