California's climate has long been dominated by cycles of intense dry conditions followed by heavy rain and snow.
But never before in recorded history has the state seen such an extreme drought-to-deluge swing.
Experts and state water officials say California is seeing more of these intense weather swings as temperatures warm, which has profound implications for the droughts and floods the state may face in the generations to come.
By Wednesday or Thursday, a new series of late-season storms is expected to vault this winter into the history books, making this year the wettest winter for California's northern Sierra Nevada in nearly a century of record-keeping. This is significant because the mountain range supplies large amounts of water for the rest of the state.
The expected milestone is all the more remarkable given that just two years before, the state was experiencing record dry conditions.
"We went from a driest-on-record scenario to a wettest-on-record scenario," said David Rizzardo, chief of the snow survey section at the California Department of Water Resources.
The extreme cycles of dry and wet weather appear to have been intensifying over the last three decades.
"When you look at the other five wettest years other than this one, the earliest of those is 1982," Rizzardo said. "When you look at the snowpack, the three driest years on record are 2015, 1991, and 1977."
The shift has coincided with increases in California temperatures that scientists say began about 1980.
"The dry periods are drier and the wet periods are wetter," said Jeffrey Mount, a water expert and senior fellow at the Public Policy Institute of California. "That is consistent with what the climate simulations are suggesting would be a consequence for California under a warming planet."
Warming global temperatures can have a profound effect on weather patterns across the planet. Changing the distribution of warmth in the ocean drives changes in the atmosphere, which ultimately decides how much precipitation gets to California, Mount said.
Warm weather worsened the most recent five-year drought, which included the driest four-year period on record in terms of statewide precipitation. California's first-, second- and third-hottest years on record, in terms of statewide average temperatures, were 2014, 2015 and 2016. And it's no coincidence that California's extreme water supply woes coincided with hot weather.
Warm temperatures in 2015 made the precipitation that did fall drop as rain instead of snow. Some rain that fell in the early part of that winter had to be flushed out to sea to keep space available in reservoirs just in case flooding came later. By spring 2015, the Sierra and Cascades produced a dubious historical record — the smallest snowpack on record, just 5% of average.
And this winter's near disaster at the overflowing Lake Oroville was in part caused by warm storms too. Exceptional water flows into the state's second-largest reservoir came not only from a constant stream of "atmospheric river" storms that happened to strike California but also because so much precipitation was coming down as warmer rain. Colder snow would not have posed an immediate flood risk.
California water officials have been discussing how warming will affect the state's water system. Now some officials believe they will have to change the infrastructure — such as building or raising dams and constructing two giant tunnels underneath the confluence of the state's two largest rivers — to deal with more precipitation falling as rain and snow melting more quickly.
Not everyone is convinced that the evidence is in that climate change is responsible for extreme swings between drought and deluge.
After all, humans have only been recording rainfall and the snowpack for a relatively short period of time in California. "I think the evidence is not very conclusive. But this surely bears watching over the coming years," said Dan Cayan of the Scripps Institution of Oceanography at UC San Diego.
"Whether this is occurring because of climate change or because we're unlucky kind of doesn't matter, because we have to deal with it either way," said Jay Lund, director for the Center for Watershed Sciences at UC Davis.
In Sierras, a winter that won’t end
Two years ago, the lack of snow left locals in Soda Springs and many other parts of the Sierra stunned and anxious.
The drought hurt ski resorts and changed the landscape of the Sierras. In some areas, trees died at an alarming rate. In others, the typically snow-capped mountains were bare and dry.
This winter, however, many residents say they've never seen so much snow.
As of Tuesday, an astonishing 87.7 inches of precipitation across a zone of eight stations in the northern Sierra has been recorded since October. That's just shy of the 88.5 inches recorded by the conclusion of the 1982-83 rain year.
"There's just been too many road closures, too many power outages, and just too much snow and nowhere to put it," said Janet Tuttle, who with her husband owns Donner Ski Ranch, one of the oldest ski resorts in the state. She had a better season financially in the very ordinary weather of last year.
Kelley Bernard, 37, didn't spend the winter here by choice. She was reassigned by the U.S. Postal Service a year and a half ago to singlehandedly staff the Soda Springs-Norden office where some 500 mountaintop residents collect their mail.
She has made the 30-mile, 4,300-foot ascent from snow-less Colfax every day in a family van, even those days when Interstate 80 was closed by blinding storms. The first time she put on her new tire chains, it took her 45 minutes to finish one tire, "and I cried, calling my supervisor, saying, 'I can't do this!'"
More than 750 inches of snow later, Bernard has not missed a single day. She has videos of herself sitting in terror in the minivan, stuck in a white-out with snow up to the axles. She can slap chains on both wheels now in less than seven minutes.
"So it's been a blessing," she said from behind the mail counter. "I never thought I could be this tough."
More water — until the next dry spell
The intense winter prompted Gov. Jerry Brown last week to finally declare the drought over in all counties except Fresno, Kings, Tulare and Tuolumne, where diminished groundwater levels still require a need for emergency drinking water. But right now, the above-ground water supply is much improved for most parts of the state.
Many of California's reservoirs are healthy and full. Lake Shasta, California's largest reservoir, is 93% full. San Luis Reservoir, an important holding area for water that will later be sent to Southern California, is at 98% of capacity.
The Metropolitan Water District of Southern California is hoping to add 1 million acre-feet of water to its so-called dry-year storage. That would get its total storage up to 2.3 million acre-feet, which would almost get the district's storage up to its high point in 2012, said Demetri Polyzos, senior water resource management engineer for the MWD.
That would last a few years if consecutive dry years return to California.
The next drought, officials say, could be just around the corner.
Times staff writer Lin reported from Los Angeles, and St. John from Soda Springs, Calif.