DENVER, C.O. (WNCT) — People in the Denver area woke up to hazy skies on Saturday, May 20, as smoke from the dozens of wildfires burning in Northeast Canada drifted south.

The Colorado Department of Public Health and Environment issued an air quality health advisory, warning residents to stay indoors if smoke became thick. Smoke would be most present during Saturday morning, the National Weather Service said.

This footage by Twitter user @oatmilk_crybaby shows fog-like smoke obscuring structures and reducing road visibility in Highlands Ranch, near Denver.

The arrival of the wildfire smoke temporarily put Denver in the top 5 of cities with worst air quality in the world, local news reported, citing IQAir’s rating.