NWS Boulder said that the smoke will begin to arrive on Wednesday night and a larger and thicker plume will arrive on Thursday in the afternoon and evening.

Weather maps from NWS Boulder show the majority of the smoke arriving from southern California near Los Angeles County. The area is currently experiencing three wildfires known as the Bridge Fire, Line Fire and Airport Fire.

Bridge Fire

This fire sparked on Sept. 8 and has scaled exponentially since then, growing to 47,904 acres across two counties. The fire has caused a large number of evacuations across Los Angeles and San Bernardino with thousands of structures under threat from the blaze. The cause of the fire is under investigation and is currently at 0% containment as of Wednesday afternoon.

Line Fire

The Line Fire was started on Sept. 5 along Base Line Road and Alpin Street in Highland, California. The fire has grown to 34,659 acres and is 14% contained in San Bernardino County. It has also forced a high amount of closures and evacuations with thousands of structures threatened. The San Bernardino County Sheriff's Office released on X that they have made an arrest for arson in connection to the Line Fire.

Airport Fire

The third fire, the Airport Fire, is located in Orange County and Riverside. Its current estimated size as of Wednesday afternoon is 22,376 acres with 0% containment. The fire was started on Sept. 9 and the cause is still under investigation. Most evacuations from this fire have taken place in Riverside with the amount in Orange County rising.

The smoke from the California wildfires is expected to linger in Colorado through Friday and could potentially affect air quality across the state. In July, smoke from wildfires in Canada and western states caused Denver to have hazy skies and some of the worst air quality among major U.S. cities.