(Image: fire.airnow.gov, June 12, 2020) 

Smoke is hanging over much of the U.S. Southwest because of wildfires in Mexico, Arizona and New Mexico.

In California, the AirNow map of the U.S. Air Quality Index shows heavy smoke from the Mexican border over the San Diego and Los Angeles areas and extending to Visalia in the Central Valley.

The principal cause is a cluster of wildires east of Tijuana, Mexico.

A prescribed burn in the area of Calaveras Big Trees State Park is creating a smaller plume that extends to the Lake Tahoe area. That burning is expected to continue until Monday. Highway 4 remains open.

The largest fire in California is the Lime Fire, which has burned 900 acres in Ventura County since Wednesday afternoon. On Friday at 9 a.m., it was 30 percent contained. An evacuation order has been lifted, but a warning remains in effect near Lake Piru, 12 miles west of Santa Clarita.

The Southwest’s heaviest smoke, with an air quality index of 500, was reported Friday morning in New Mexico’s Gila National Forest, where the lightning-sparked Good Turkey Fire has burned 7,640 acres. That air quality is considered hazardous, and outdoor physical activity is discouraged for everyone.

In Arizona, the Bighorn Fire has burned 4,800 acres and is threatening hundreds of homes in the suburbs of Tucson. It was started by a lightning strike last Friday.