Smoke from Yosemite fire drifts into central California

A fire truck drives past burning trees as firefighters continue to battle the Rim Fire near Yosemite National Park, Calif., on Monday, Aug. 26, 2013. Crews working to contain one of California's largest-ever wildfires gained some ground Monday against the flames threatening San Francisco's water supply, several towns near Yosemite National Park and historic giant sequoias. (AP Photo/Jae C. Hong)

August 30, 2013 3:42:50 PM PDT
Central California air officials say a shift in wind has sent smoke from the massive forest fire burning in and around Yosemite National Park down into six San Joaquin Valley counties.

The regional Air Pollution Control District on Friday issued a health cautionary statement for San Joaquin, Stanislaus, Merced, Madera, Fresno and Tulare counties, especially for foothill and mountain areas.

Officials say the impacts from the 315-square-mile blaze will be felt throughout the Labor Day weekend.

Previously, the fire prompted unhealthy air alerts in Nevada.

Residents who see or smell smoke should stay inside, especially people with heart of lung problems, older adults and children.

The 2-week-old fire is now the largest to date this year in the U.S. It's 32 percent contained.