The benefits from a welcome splash of rain in February and early March rapidly diminished across California, and Sonoma County returned to "extreme drought" condition, the U.S. Drought Monitor said this week.

Redwood Empire reservoirs got a small boost from the rain, but water officials said the region remains in a "critical dry year" with a bit more precipitation expected in the middle of next week, when Santa Rosa could get up to one-quarter inch.

Sonoma County's hillsides and grasslands are once again bright green, dashed with yellow mustard blossoms, but it's "basically fool's gold," said Randy Adkins, an Accuweather meteorologist.

"In the grand scheme of things it's not worth anything," he said.

The county and part of the northern Sierra Nevada, both downgraded to "moderate drought" a week ago, returned to the next-most-severe rating following a stretch of sunny weather, the Drought Monitor said.

"Unseasonable warmth and dryness" boosted water demands and depleted snowpacks in California and the Southwest, the monitor said.

In Thursday's report, nearly 72 percent of California had "extreme drought" or "exceptional drought" — the top two driest conditions.

The only exceptions were the far northern end of the state, the desert region of southern California and a thin band east of the central and southern Sierra.

A week ago, 66 percent of California had the two driest conditions.

Santa Rosa received 9.34 inches of rain in February, significantly better than the 30-year average of 6.02 inches for the month, according to Accuweather.

The first week of March added 0.77 inches, with the last rain falling March 6.

(You can reach Staff Writer Guy Kovner at 521-5457 or guy.kovner@pressdemocrat.com.)