Smoke from two wildfires burning near Big Sur is pushing hazy skies and unhealthy air at times into Walnut Creek and the wider Bay Area through Tuesday, Sept. 1.

The Bay Area Air Quality Management District (BAAQMD) issued the wildfire smoke advisory on Monday, Aug. 31, warning that residents may notice the smell of smoke and reduced visibility. Air quality could reach unhealthy levels at times on both days, according to Local News Matters, which first reported the advisory.

The smoke is tied to two fires in Monterey County: the Timber Fire, which started Aug. 8 and has burned nearly 19,000 acres, and the Plaskett Fire, which broke out Aug. 26 south of the Timber Fire and measured less than 200 acres as of Aug. 27. Those acreage figures are from late August; updated numbers were not available as of Sept. 1.

The Timber Fire forced hundreds of residents near Big Sur to evacuate. The Plaskett Fire also prompted evacuations after it started east of Los Burros Road, according to KAZU.

This is the second time in a week that Big Sur fire smoke has drifted over Contra Costa County. NOAA satellite imagery showed heavy smoke from the Timber Fire traveling northward into the area, as Claycord reported on Aug. 25.

NBC Bay Area meteorologist Rob Mayeda noted on X on Aug. 31 that the region was tracking wildfire smoke alongside a shift to cooler, cloudier weather to start September.

@RobMayeda: "September will be starting off much cooler than average with drizzle and showers at times. We're also tracking wildfire smoke and weekend rain chances to our south with a connection to the tropics (stay tuned on that)"

The Walnut Creek School District said on its website that it uses AirNow, the EPA-based air quality index, as its primary monitoring tool. The district has also installed MERV 13 air filters in all its facilities, which it says capture PM2.5 smoke particles.

The BAAQMD has not announced whether the advisory will be extended past Tuesday. Residents can check current air quality readings at AirNow.gov or contact the district at (415) 749-4900.