california drought

Map: See How a Parade of Early Winter Storms Improved Drought Conditions in California

All of California remains is some level of drought, but conditions improved dramatically in the two most severe drought categories.

NBCUniversal Media, LLC Around the country, people rely on these piles of snow for their water supply. What is a snowpack, and how else does it impact you?

A series of early winter storms that brought days of rain and snow to California helped improve conditions in the drought-stricken state.

All of California remains is some level of drought this week, but conditions improved significantly in the two most severe categories.

The weekly report released Thursday shows exceptional drought was nearly erased after 23 percent of the state was under the most severe category one week ago. Nearly 33 percent of the state is in extreme drought, down from 79 percent last week.

Three months ago, that figure was at 88 percent.

US Drought Monitor
The US Drought Monitor map for the last week of 2021.

The storms fueled by a band of moisture over the Pacific began the week of Christmas and continued to usher in rain and mountain snow this week. The report was updated early Dec. 28, so it does not factor in all precipitation received this week.

"A persistent pattern over the North Pacific and western North America maintained a continuation of frequent storms affecting the West Coast through late December," the Drought Monitor statement said. "Seven-day precipitation from December 21-27 exceeded 2 inches, liquid equivalent, across much of California along with western portions of Oregon and Washington.

US Drought Monitor
These maps show drought conditions according to the US Drought Monitor reports released Dec. 30 (right) and the previous week.

During the past two weeks, precipitation has averaged 150 to 300 percent of normal or more throughout nearly all of California, the report stated.

"This wet pattern during mid to late December has also been accompanied by below normal temperatures (-2 to -6 degrees F) across California and the Pacific Northwest."

The Central Sierra snow lab has observed 193.7 inches of snowfall this month, which is a December record, topping the previous record of 179 inches set in 1970.

California's mountain snow holds 160% of the water it normally does this time of year, state water officials announced Thursday.

"Given the favorable snowpack and heavy precipitation during December, additional improvements may be warranted for California during subsequent weeks," the Drought Monitor report said. 

Caltrans
The State Highway 89 roundabout in Tahoe City is pictured Thursday Dec. 30, 2021.
NBCLA
The 5 Freeway was closed north of Los Angeles Thursday Dec. 30, 2021.
FOREST FALLS, CA – DECEMBER 28, 2021: Sam Richey, 15, of Forest Falls gets some air-time while using a Boogey board to sled on fresh snow from Mondays winter storm on December 28, 2021 in Forest Falls, California.(Gina Ferazzi / Los Angeles Times via Getty Images)
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Tustin, CA – December 26: Sun and clouds paint the sky over Orange County on Sunday, December 26, 2021 as storms are expected to close out the year. Rain and snowfall of 4 to 8 inches is anticipated at elevations above 4,000 feet and up to 16 inches above 6,500 feet Monday into Tuesday. (Photo by Mindy Schauer/Digital First Media/Orange County Register via Getty Images)
NBCLA
Snow in the mountains east of Los Angeles Wednesday Dec. 29, 2021.
FOREST FALLS, CA – DECEMBER 28, 2021: A man takes a selfie amidst the snow covered San Bernardino National Forest after Mondays winter storm dropped snow to the 5,000 foot level blanketing Forest Falls in a white winter scene on December 28, 2021 in Forest Falls, California.(Gina Ferazzi / Los Angeles Times via Getty Images)
Torrance, CA – December 28: With a break from the rain but cold temperatures and bright sun, the ocean almost looks like snow at the beach in Torrance on Tuesday, December 28, 2021. Showers are forecasted to return Wednsneday and Thursday but New Year”u2019s Eve celebrations should be under clear skies. (Photo by Brittany Murray/MediaNews Group/Long Beach Press-Telegram via Getty Images)
CHP
A storm closes part of Interstate 80 in the Sierra Nevada Mountains Dec. 25, 2021.
Caltrans
Caples Lake Maintenance crews clear snow on State Route 88 on Christmas Eve in Alpine County.
Caltrans
Caltrans crews clear snow in the mountains of Inyo County on Christmas Day.
Silverado Canyon, CA – December 24: A mudslide-covered propane tank sits along Silverado Canyon Road in Silverado, located in eastern Orange County, following an overnight storm, on Friday, December 24, 2021. The December 2020 Bond fire burned much of the the area and left the hills above the canyon barren and vulnerable rock-filled mudslides. (Photo by Mark Rightmire/MediaNews Group/Orange County Register via Getty Images)
SILVERADO CANYON, CA – DECEMBER 23: Jay Parker, 40, stands where his yard was washed away, the hot tub covered with mud and oak trees were toppled by a flash flood during last weeks storm along the 28000 block of Silverado Canyon Road on Thursday, Dec. 23, 2021 in Silverado Canyon, CA. (Gary Coronado / Los Angeles Times via Getty Images)
Caltrans
Caltrans crews clear snow in the mountains of Inyo County on Christmas Day.
Los Angeles, CA – December 23: Cars drive through a rain flooded intersection at Chastsworth St and Haskell Ave in Granada Hills, CA, Thursday, Dec 23, 2021. (Photo by Hans Gutknecht/MediaNews Group/Los Angeles Daily News via Getty Images)
Los Angeles, CA – December 23: A pedestrian makes his way along Van Nuys Blvd at Arleta Ave in Arleta, Thursday, Dec 23, 2021. (Photo by Hans Gutknecht/MediaNews Group/Los Angeles Daily News via Getty Images)
LOS ANGELES, CA – DECEMBER 21: Snowcapped mountains are seen in the distance from City Terrace on the first day of winter in Pasadena on Tuesday, Dec. 21, 2021 in Los Angeles, CA. A series of storms spinning off the coast of Northern California are gathering strength and will soon begin moving toward the lower part of the state, the National Weather Service said. (Dania Maxwell / Los Angeles Times via Getty Images)
Calttrans
A damaged stretch of State Route 18 in the San Bernardino County mountains Friday Dec. 24, 2021.
Caltrans
Part of State Route 18 in the San Bernardino County mountains was closed in both directions.
Caltrans
A view of traffic on Interstate 80 near Donner Summit on Dec. 24, 2021.
Silverado Canyon, CA – December 24: Crews work at cutting up a large tree that fell across Silverado Canyon Road in Silverado, located in eastern Orange County, early Friday, December 24, 2021, following overnight storm that brought heavy rain and wind, knocking over a utility pole as it fell. The canyon areas are under mandatory evacuations following overnight storms that brought heavy rain and mudslides. The December 2020 Bond fire burned much of the the area and left the hills barren and vulnerable rock-filled mudslides. (Photo by Mark Rightmire/MediaNews Group/Orange County Register via Getty Images)
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SANTA MONICA, CA – DECEMBER 24, 2021 – – A passing storm makes its way above people who play in the surf on Christmas Eve in Santa Monica on December 24, 2021. (Genaro Molina / Los Angeles Times via Getty Images)
Silverado Canyon, CA – December 24: An evacuation order sign on East Santiago Canyon Road in Orange informs motorists that the canyon areas of eastern Orange County are under mandatory evacuations following overnight storms that brought heavy rain and mudslides to the area, on Friday, December 24, 2021. The December 2020 Bond fire burned much of the the area and left the hills above the canyon areas barren and vulnerable rock-filled mudslides. (Photo by Mark Rightmire/MediaNews Group/Orange County Register via Getty Images)
OAKLAND, CALIFORNIA – DECEMBER 23: Workers clear a mudslide from a double lot in the 6300 block of Westover Drive in Oakland, Calif., on Thursday, Dec. 23, 2021. More rain is expected through the holiday weekend according to the National Weather Service. (Jane Tyska/Digital First Media/East Bay Times via Getty Images)
Caltrans
Snow covers Interstate 80 in Northern California’s Placer County.
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OAKLAND, CALIFORNIA – DECEMBER 23: Storm clouds are seen over San Francisco in this view from Oakland, Calif., on Thursday, Dec. 23, 2021. (Jane Tyska/Digital First Media/East Bay Times via Getty Images)
Jessica Samet
A downed pine tree in Cheviot Hills Friday Dec. 24, 2021
Caltrans
A view of the 101 Freeway in San Luis Obispo on Dec. 23, 2021.
Sequoia and Kings Canyon National Parks
A rockslide in Sequoia National Park.
Sequoia and Kings Canyon National Parks
A snowy scene in Grant Grove in Kings Canyon National Park.
AP Photo/Jeff Chiu
Pedestrians carry umbrellas as they walk past a large holiday tree outside of the Chase Center in San Francisco, Dec. 22, 2021.

Droughts are common in California, where dry spells are often followed by wet winters that replenish the state's critical snowpack and water reservoirs. And it takes more than a lot of rain and snow in one shot to ease drought conditions.

The state is “definitely not out of the woods quite yet," said Sean de Guzman, manager of the snow surveys and water supply forecasting for the California Department of Water Resources.

Prolonged hot and dry conditions over moths and years means water evaporates at a faster rate from reservoirs and the Sierra Nevada snowpack that feeds them. The snowpack usually melts in spring or early summer, then that water flows into the state’s vast storage and distribution system.

About a third of California's water supply comes from snow as it melts and flows down from the Sierra Nevada and the Shasta-Trinity mountain range in northern California.

California has more than 500 reservoirs, which were 50% lower than they should be at the start of June. These photos show the dramatic impact of the current dry spell at California’s lakes and reservoirs. 

California's Mediterranean-style climate means the summers are always dry and the winters are not always wet. The state's reservoirs act as a savings account, storing water in the wet years to help the state survive during the dry ones.

Last year was the third driest on record in terms of precipitation.

Drought is generally defined as a period of drier-than-normal conditions resulting in water-related problems. That period can be days, weeks, months and years.

The term can have different meanings, depending on how water users are affected by water deficiencies. In a state of 40 million people, that's a lot of water users impacted in different ways by dry spells.

Droughts have been classified into the following:

  • Meteorological drought means a lack of precipitation.
  • Agricultural drought describes a lack of soil moisture.
  • Hydrologic drought indicates reduced streamflow or groundwater levels.

California recently went through a five-year event from 2012-2016. Other notable historical droughts included 2007-09, 1987-92, 1976-77, and off-and-on dry spells of more than a decade in the 1920s and 1930s.