The Ukiah Daily Journal reports that the county's Board of Supervisors on Tuesday voted unanimously to make the declaration, citing an "imminent threat of disaster" from drought conditions.
The state Department of Water Resources said Mendocino is the first to request state drought assistance.
Officials hope the declaration will result in state funds and assistance in developing a drought plan.
Gov. Jerry Brown has convened a task force to help decide if a statewide drought emergency is warranted.
State water managers say they will be able to deliver just 5 percent of the water sought by municipal agencies and nearly a million acres of farmland.
Caltrans is worried about the possibility of dead trees falling onto some California highways. The agency has already removed 107,000 trees. Now the agency is getting ready to remove another 54,000 trees, including some on private land.
Sacramento city council voted in favor of a proposal that makes some drought watering restrictions permanent.
Tuesday marks the start of a shortened commercial salmon fishing season in the waters off San Francisco. A smaller salmon population is one effect of the drought that could persist for years.
A wealth of weather and climate data and the jobs of the scientists who analyze it may be at risk under President Trump’s budget proposal.
The Central Sierra Nevada snowpack this year is larger than the previous four years combined, according to new data from NASA.