Wildland fire naturally occurs in and near the Mono Basin from spring through fall. Yosemite National Park immediately upwind often has several lightning fires burning at any time during the summer. Fires as far away as the coast can turn Mono Basin skies smoky.

9/4/09 Update
Tioga Road is closed at least through the holiday weekend from Crane Flat to White Wolf. The Big Meadow Fire is almost fully contained and the smoke in the Mono Basin is gone!
Updates

8/31/09 Big Meadow Fire Update
At 3:30 pm today Tioga Road closed between White Wolf and Crane Flat due to smoke. Prior to this closure the road closed at night and had controlled traffic during the day. If the road re-opens, expect these restrictions to resume.
Updates
Blog and Photos

8/28/09 Big Meadow Fire Update
The Big Meadow Fire grew to over 2,000 acres yesterday and Big Oak Flat Road (access between Hwy 120 and Yosemite Valley) remains closed. There is an alternate route via Hwy 49 to Yosemite Valley that takes about 3 hours. Foresta and Crane Flat Campground are evacuated. NPS is considering closing Tioga Road (Hwy 120) at White Wolf, although the road remains open at this time. The smoke is moving north and is not yet affecting the Mono Basin. The latest info is here.

Yosemite National Park
Yosemite National Park Current Fire Activity
Yosemite National Park Current Air Quality and Smoke Monitoring

California
Inyo National Forest Fire Information
California Incidents
State Fire Information
Daily satellite image