The cloud of smoke that engulfed the Denver metro area over the weekend is expected to linger over the coming days, officials said.

On Saturday, Denver’s air quality ranked the worst in the world among major cities, according to IQAir. Saturday’s air quality index reached 192, within the Environmental Protection Agency’s “unhealthy” category.

“Unhealthy” air quality means the air can cause adverse health effects for all people and serious effects for sensitive groups. A “good” air quality index is 0-50, “moderate” is 51-100 and “unhealthy for sensitive groups” is 101-150.

On Sunday morning, Denver’s air quality ranking dipped to second worst in the world, with a score of 164, and reached sixth worst by the evening, with a score of 129. However, this progress is not expected to continue.

Denver's metro air quality worst in the world Saturday

Despite small improvements, Denver is expected to receive another round of even thicker smoke throughout the day Monday, according to the National Weather Service in Boulder.

Russell Danielson, a meteorologist with the weather service, said Saturday, Sunday and Monday would be “some of the smokiest days of the summer.” Though conditions may improve after Monday, the air quality will still be poor, Danielson said.

Danielson said the smoke is from an upper-level low pressure system moving from California and Canada, where large wildfires are currently burning, into Colorado’s Front Range.

The smoke is expected to last for the next few days and may begin to clear by the end of the week, according to the state health agency. However, hazy and smoky conditions could become the new normal until the end of the fire season.

Wildfire smoke exacerbates health conditions, contributes to more deaths, and it's getting worse

Dan Welsch, an air quality meteorologist with the state health department, told The Denver Gazette last week that bad conditions will persist until the fires to the west become more contained.

“Current projections are unfortunately showing more of the same for at least the foreseeable future,” Welsh said.

While Denver’s air quality is in the “unhealthy” range, residents are urged to avoid outdoor exercise, keep windows closed and wear face masks when outdoors.