What's causing hazy St. Louis-area skylines?

ST. LOUIS - Over the next few days, you may notice some hazier skies across the St. Louis region. And there's a scientific reason for that.

Smoke from wildfires burning in Canada is drifting south and settling high in the atmosphere, creating hazy conditions for many Midwestern U.S. states.

Around St. Louis, the smoke began to move in Friday afternoon. What started as a day of mostly clear blue skies became increasingly muted by sunset. The next few days could follow similar patterns.

The National Weather Service says smoke concentrations will likely remain low on Saturday but could linger into Sunday evening or Monday morning in St. Louis, depending on how an ongoing jet stream behaves. So far this weekend, higher concentrations of smoke have stayed north or moved east of the St. Louis metro.

The smoke stems from more than 160 wildfires burning across Canada, many of them classified as out of control. As the fires intensify, a jet stream brings heavy winds that help carry the smoke from northern forests across the border and as far south as the Mississippi River Valley.

Fortunately, most of the smoke in the St. Louis region is expected to stay high in the atmosphere, meaning it's unlikely to cause major issues to air quality or visibility. Still, there's a chance for hazy skylines over the next few days, especially during sunrise and sunset hours.

While the wildfire smoke impacts may be mild locally, the broader situation is more serious. Canada has declared a state of emergency in several provinces and has called in military assistance with long-range impacts on air quality still unfolding.

Air quality forecasts for St. Louis and other parts of the United States can be found at AirNow.gov, a resource spearheaded by the Environmental Protection Agency.