Certain places on the East Coast of the United States are feeling the effects of Southern Oregon’s wildfires more than Portland is.

Yesterday, smoke from the West Coast’s dozens of wildfires, including the massive Bootleg Fire in Southern Oregon, reached states on the Atlantic Coast, causing dangerous air quality conditions.

The Bootleg Fire has been spreading for over two weeks now and has eclipsed almost 400,000 acres. It’s only 32% contained. Droves of firefighters are battling it, including 13 from the Portland metro area who work 12-hour shifts throughout the night.

Dr. Paul Loikith is director of the Climate Science Lab, an associate professor in the geology department at Portland State University, and an expert on extreme weather. He explains that the smoke from Oregon’s wildfires is being carried to the East Coast by heavy winds moving east.

“The simplest way to put it is that air primarily moves from west to east. It doesn’t go in a straight line, there are wiggles and curves, but air primarily travels from west to east. So the smoke gets caught up in pretty strong winds above the earth’s surface and transports the smoke to the East Coast,” Loikith explains.

Right now, smoke emitted by the fires is traveling northeast through Montana and Idaho, dipping into central Canada, then curving again to the east, looping down through the Great Lakes, and then once again going east toward places like Philadelphia and Washington, D.C.

Smoke traveled to the East Coast last September when wildfires raged in Oregon, but the smoke didn’t descend low enough on the East Coast to cause the same amount of air quality damage as it is currently.

Thousands of people have evacuated since the onset of the Bootleg Fire.