Colorado's famously crystal clear skies appear noticeably less blue Thursday.

Mike Silverstein, deputy director of the Colorado Air Control Division in Denver, says the haze is caused by smoke from wildfires in Colorado and the West.

Wildfires are currently burning in Moffat County in northwestern Colorado and near Meeker in Rio Blanco County.

"Because of the fires, there is a lot of fine particulate matter in the air obscuring visibility and exacerbating our usual pollution."

An additional contributor to the haze, Silverstein noted, is the current temperature inversion over the Front Range. As a result, emissions in the air are trapped here until the area gets some strong breezes or rain.

As a result, the Colorado Department of Public Health and Environment has issued an ozone action alert for the Front Range that will be in effect at least until 4 p.m. today. The ozone level is expected to climb past the moderate range through the day. Because particulate levels are likely to rise to the unhealthy-for-sensitive category by this afternoon, people with respiratory or heart problems, the elderly and small children are advised to avoid prolonged exertion outdoors during the next 24 hours.

According to the Colorado Air Control Division, the conditions may improve early next week when a predicted cold front moves in.

Information: colorado.gov/airquality/advisory.aspx