Thick smoke will cover much of Eastern Washington and the Idaho Panhandle on Saturday and Sunday, bringing with it air-quality alerts from the National Weather Service.

Laura Watson, Washington state Department of Ecology director, said she expects the smoke to reach Spokane by Saturday afternoon.

A massive cloud of smoke approached Washington on Thursday, bringing hazy skies to Eastern Washington on Friday. But NWS meteorologists expect higher impacts from the smoke over the weekend, a rare event that could slow commerce.

That smoke also could irritate lungs and make residents of the region more prone to lung infections, including COVID-19, according to a news release from the Panhandle Health District.

In a Friday news conference, Gov. Jay Inslee urged Washingtonians to stay home if possible.

The biggest concern is small particles in the air, Watson said.

“Just because you can’t see it, doesn’t mean you can’t breathe it,” she said.

The Panhandle Health District and the Idaho Department of Environmental Quality issued a Wildfire Smoke Advisory on Friday for Boundary, Bonner, Kootenai, Shoshone and Benewah counties.

How the smoke will appear in Spokane and surrounding areas is hard to predict, said NWS meteor- ologist Steven Van Horn.

He said though it’s typical to see smoke during peak fire season, this event is unique because it will cover such a large area. Whether Eastern Washington and North Idaho will see auburn skies like those in Oregon and Northern California isn’t easy to predict, but smoke traveling this way from the Tri-Cities gives meteorologists an idea.

“The smoke is fairly thick that’s coming through the Tri-Cities,” Van Horn said, looking at footage in the area. “It’s almost like fog coming through, except it’s just smoke.”

Poor air quality will escalate from being unhealthy for sensitive people to “hazardous,” according to the Spokane Regional Clean Air Agency.

This rating affects everyone, not just those sensitive to poor air quality, Van Horn said.

The symptoms of smoke inhalation and COVID-19 are similar, State Health Officer Dr. Kathy Lofy said. Symptoms of both can include coughing, wheezing and difficulty breathing.

During previous wildfire seasons, Lofy said there have been increases in visits to emergency rooms due to smoke inhalation, but the state has enough COVID-19 testing ability to allow patients and health providers to tell which condition they are dealing with.

The Washington Emergency Management Division recommended that Washingtonians secure air filters to box fans to filter air in their homes.

The smoke could begin to clear out Monday, according to the National Weather Service. Some fires in the Northwest could see rain, which would decrease fire activity and smoke output.

S-R reporter Lauren Demkovich contributed to this report.