DENVER (AP) — Smoke from wildfires burning in California and other parts of the U.S. West continued to flow into parts of Colorado and Utah on Sunday.

Sunday, the Colorado Department of Public Health and Environment ranked the air quality in many areas of the state as unhealthy.

Conditions in the Denver area were relatively better than on Saturday but thicker smoke was expected Monday, the National Weather Service in Boulder said.

In Utah, northern and central parts of the state were expected to remain smoky at least through midweek, according to the National Weather Service in Salt Lake City.

The smoke has made the air quality in Denver and Salt Lake City among the worst in the world, according to air quality tracking website IQAir.