Thick smoke from wildfires across the west and northwest are plaguing multiple states, with thick smoke and dangerous air quality, including Colorado.

Visibility across the I-25 corridor was reduced to 3 miles to 5 miles Monday morning.

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An Air Quality Health Advisory for Wildfire Smoke is in effect for northeastern Colorado -- including Denver, Boulder, Fort Collins and Greeley -- until 4 pm Monday.

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Air quality has fluctuated Monday from moderate to unhealthy. People with heart or lung disease, respiratory issues, older adults and children should take it easy outdoors.

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Expect slow improvement as we head into the overnight and Tuesday, as a more west/southwest flow develops. It will be gradual, with smoke near the ground along the I-25 corridor especially slow to move out.

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