What is the air quality index across the US?

Polluted air will remain a threat Friday for millions of Americans across the eastern United States as the Canadian wildfires continue to send smoke billowing across the region, tinging the skies with a hazy − sometimes orange − glow.

With air quality alerts still in place, residents from Michigan, Ohio, the Northeast and the Mid-Atlantic are still being advised to remain indoors as much as possible. In some cases, people are advised to wear masks to filter out harmful particles that make the air unsafe to breathe.

Experts are warning that the weather pattern that’s bringing the Canadian smoke into the eastern U.S. is only the beginning as Canadian wildfires become more rampant. While the weather pattern isn’t unusual, meteorologists say what’s notable is the volume of smoke being produced due to the historic number of fires.