Smoke from a planned burn in Marin County blanketed parts of Orinda and Lafayette on Tuesday, Aug. 25, prompting the City of Orinda to advise smoke-sensitive residents to limit outdoor activity.

There was no fire in Orinda. The haze came from a prescribed burn in the Mt. Tamalpais Watershed near Bon Tempe Reservoir, west of Fairfax, managed by the Marin County Fire Department in coordination with Marin Water. The burn, which could cover up to 79 acres near Sky Oaks Ranger Station, is part of ongoing vegetation management aimed at reducing wildfire fuel on the mountain, according to a Marin County news release.

The city posted its advisory on X, telling residents the smoke had drifted in from a Marin County controlled burn and that no active fire was burning locally.

Orinda residents were among the first in the region to report the smoke's arrival, according to News24-680. Reports quickly followed from Lafayette, Walnut Creek and Concord, with multiple callers expressing concern that something was burning nearby. Local fire crews were dispatched to search areas generating the most calls but found no fires. Officials attributed the haze to drift smoke caught in an atmospheric inversion.

Marin County officials asked the public not to call 911 to report smoke from the burn area, to keep dispatch lines open for actual emergencies. The burns were conducted in compliance with Bay Area Air Quality Management District requirements.

A second prescribed burn is planned for today, Wednesday, Aug. 26, in the Pine Point area near Bon Tempe Reservoir, covering up to 44 acres. Together, the two burns could treat up to 123 acres of watershed land. Both burns are tentative, depending on favorable weather, fuel conditions and air quality, and could continue for additional days if needed to finish the planned work, according to the Marin County news release.

During burn operations, the Bon Tempe parking lot, Bon Tempe Road and Bon Tempe Channel Road North will be closed. Sky Oaks Road will stay open but may see short delays and temporary lane closures as fire engines patrol the burn perimeter.

Residents who want direct updates can sign up for prescribed-burn text alerts through AlertMarin at Emergency.MarinCounty.gov. The City of Orinda posted a follow-up advisory at 4:07 p.m. Wednesday, telling residents they may see smoke in the area from the ongoing prescribed burn activities in Marin.