Map: Winter Storms Wipe Out Drought in California's Central Valley

A large swath of California's agricultural Central Valley is no longer in drought after a series of atmospheric river-fueled winter storms that brought rain and snow over the past two months.

At the start of the water year in late September, the Central Valley was one of several regions facing extreme to exceptional drought, the two most severe drought categories in the weekly U.S. Drought Monitor report.

But the most recent report issued Thursday shows a stark contrast.

The Central Valley and a stretch of the California coast from western Los Angeles County to the Oregon border are no longer in drought, according to the Drought Monitor.

"There's a big change," said NBC4 forecaster Shanna Mendiola. "We don't have any drought in Central California. It's been completely wiped out by these storms."

Thirty-six percent of the state is in moderate drought, the least severe of the weekly report's four drought categories. At the start of the water year in late September, that figure was at 99.76 percent.

Only 8 percent of California is in severe drought, a significant improvement from 93 percent at the start of the water year.

The most recent Drought Monitor report includes data available up to the morning of March 14, so it does not account for precipitation recorded on the remainder of Tuesday and Wednesday. Precipitation from that storm will be included in next week's report.

More wet weather is in next week's forecast.

Storms in February and March have triggered flooding, slides and other problems throughout the state. Some 27,000 people are still under evacuation orders statewide.

As of Wednesday, an additional 61,000 people remained under evacuation warnings and emergency shelters housed more than 650 people, according to the California Governor’s Office of Emergency Services.

In Central California, a levee break along the Pajaro River caused flooding in Monterey County.

"Rain, along with melting of lower-elevation snowpack and dam releases, also led to significant water rises along many waterways in California’s Central Valley," the Drought Monitor report said. "By March 15, the San Joaquin River at Patterson, California, neared a record crest, with the water rising to within less than a foot of the February 2017 high-water mark.

The storm that arrived Tuesday is the latest in a series of February and March systems fueled by an atmospheric river. Downtown Los Angeles received 3.15 inches of rain in March as of Tuesday. That's well above the average of 2.23 inches for the entire month of March.

This is now the 14th-wettest water year for downtown Los Angeles on record at 23.99 inches. California's water year starts in October with most of the state's annual precipitation occurring during winter months, including snow that blankets the Sierra Nevada Mountains -- the state's natural water reservoir.

California has spent most of the last 15 years in drought conditions. The most recent dry spell included one of the driest late winters on record.

The state's normal wet season runs from late fall to the end of winter, but dismal precipitation left about 95 percent of California in severe drought at the start of spring last year. California recorded its driest first three months of the year on record to start 2022 and by September nearly all of California was in drought.

Much of California’s water comes from melting snow in the Sierra Nevada Mountains. In an ideal scenario, storms blanket the mountains with snow during winter, building up the natural reservoir. That snow then melts in late spring and early summer, replenishing the state's water system.

The average mid-March water equivalency of the high-elevation Sierra Nevada snowpack topped 55 inches. That's more than 220% of normal for an entire season, according to the California Department of Water Resources. 

Roughly a third of California's water each year comes from melted snow in the Sierra Nevada, a mountain range that covers the eastern part of the state. The state has complex system of canals and dams to capture that water and store it in huge reservoirs so it can be used the rest of the year when it doesn't rain or snow.

The snowpack is off to one of its best starts in 40 years.