Smoke from the Siberian wildfires also stretched over 1,200 miles on Wednesday to reach all the way to Mongolia.
The burning taiga is sending a massive plume up into the atmosphere and then over to Alaska.
Researchers looked at the relationship between wildfire smoke and hospital visits in Alaska.
Cities and towns across the West are warning residents that high levels of smoke from forest fires threaten their health, with no sign of abating. That means indoor recess and no vacuuming.