Most of Sonoma County emerges from drought, U.S. Drought Monitor says

The return of winter storms has eliminated a state of drought for nearly all of Sonoma County, with just its northeast corner still considered to be in “moderate drought,” according to the latest update from the U.S. Drought Monitor.

The shift is part of a recasting of much of the state by the Drought Monitor. Renewed rain and snowfall around California since late December left the entire Bay Area and about 89% of Sonoma County in “abnormally dry” conditions, as of Feb. 28, but no longer in drought.

The western two-thirds of Mendocino County is considered drought-free, as well as one-third of Napa County, according to the widely consulted map, a product of the National Drought Mitigation Center at the University of Nebraska at Lincoln, in partnership with the U.S. Department of Agriculture and the National Oceanic and Atmospheric Administration.

The mapping is based on data points ranging from precipitation, soil moisture and hydrological factors to agricultural, socioeconomic and ecological factors that reflect the impact of extended drought and go beyond conditions at any given moment.

It also takes into account a region’s climate history and input from local collaborators with information about specific impacts, said Curtis Riganti, a climatologist with the National Drought Mitigation Center.

With full reservoirs and area rainfall above normal for the time of year, thanks largely to a series of atmospheric rivers that drenched the region and caused areas of flooding between Dec. 26 and Jan. 17, continued references to drought have appeared out of place in recent weeks.

“With the Drought Monitor map, we’re trying to represent all of those in one map,” Riganti said. “When we’re looking at drought, we aren’t just looking at, ‘Did it rain this weekend,’ or ‘How much did it rain? Is it wet outside?’”

Both of the region’s primary reservoirs, Lake Sonoma and Lake Mendocino, are above water supply levels as of this week, with season-to-date rainfall at the Charles M. Schulz-Sonoma County Airport at 27.66 inches since Oct. 1, compared to a 30-year normal of 25.72 inches.

The normal seasonal precipitation, from Oct. 1 to Sept. 30, is 33.78 inches, the National Weather Service said.

You can reach Staff Writer Mary Callahan (she/her) at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.