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When Kamie Loeser took over as the director of water and resource conservation in Butte County, in Northern California, she was immediately tasked with navigating a once-in-a-lifetime drought.
It was October 2021. California had just seen its second-driest year on record, and Lake Oroville, a major reservoir in Butte County, was at its lowest level ever—just 22 percent of capacity.
But by the end of that month, a “bomb cyclone” atmospheric river had dumped so much water that Lake Oroville’s surface level rose by 30 feet in one week. Parts of Northern California experienced their highest single-day rainfall ever recorded.
“What you see year to year is: empty reservoir, overflowing reservoir that almost took out the spillway, empty reservoir, full reservoir, reservoir that’s on fire at its margins, empty reservoir,” said Daniel Swain, a climate scientist at UCLA and the National Center for Atmospheric Research who studies extreme weather.
Then, this summer, the Park Fire erupted near Chico, Butte County’s largest city. Quickly growing to be the fourth largest wildfire in state history, the Park Fire burned 430,000 acres and revived memories of the 2018 Camp Fire, which destroyed nearly all of the nearby town of Paradise. A separate, smaller wildfire also ignited along the banks of Lake Oroville in July, shortly after the reservoir reached full capacity for the second consecutive year.
In less than three years on the job, Loeser has dealt with drought, flooding, and fire in quick and devastating succession. It’s a pattern repeating across California and around the world as climate change intensifies extreme weather and, increasingly, drives the rapid transition from one extreme weather event to another.
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How California became the land of extremes
That phenomenon, which scientists call climate or weather whiplash, is set off by greenhouse gasses emitted by burning fossil fuels, which warm the atmosphere. Warm air can hold more water vapor than cold air, so the atmosphere gets thirstier in hot weather, sucking up extra moisture from the ground.
Dry vegetation is left behind, primed to burn if a fire ignites.
All that evaporation also means that when it rains, it pours, raising the risk of deadly flooding and landslides. At the same time, those downpours can accelerate plant growth—leaving more fuel to burn when extreme heat returns to dry out the landscape.
“The worst climate for wildfire is not one that gets perennially drier,” Swain said. “If you alternate getting wetter and dryer, while it’s getting hotter, you have enough water in the system at least every few years to regrow everything and then burn it off again.”
Recent wildfires in California have largely followed that pattern. After record-breaking fire years amid intense drought in 2020 and 2021, wet conditions brought mild fire seasons in 2022 and 2023. The Park Fire, along with multiple fires near Los Angeles, shattered hopes for another calm year in 2024.
Wildfires also increase the risk of landslides and flooding after they pass through. Burnt vegetation has a diminished ability to hold soil in place or absorb water, and ash that blankets a burn zone allows water to slide downhill without sinking into the earth.
“There are no trees or vegetation to slow runoff, and there’s increased sediment,” Loeser said. “As a result, we have increases in flooding after wildfires.”
This yo-yo effect has drenched and parched California repeatedly over the last several years. Torrential rainstorms inundated the state in December 2021, followed immediately by the driest January, February, and March in over 100 years. The following winter brought heavy precipitation, and by April 2023 statewide snowpack swelled to 237 percent of average.
These rapid transitions between extreme weather events are not confined to California. Southeast Texas was hit this summer by Hurricane Beryl, only to see the storm followed immediately by a powerful heatwave. Nine of 22 deaths attributed to Beryl in Harris County, which includes Houston, were tied to heat—storm damage left more than one million residents without electricity or air conditioning as temperatures exceeded 100 degrees, according to the Department of Health and Human Services.
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Extreme weather persists in winter
Scientists expect that warmer temperatures will cause more winter precipitation to fall as rain instead of snow. Frances Davenport, a researcher at Colorado State University who studies extreme precipitation, said more rainfall in winter, California’s wet season, could translate to more floods.
“Snow is like an annual reservoir that releases water during summer, when there’s higher water demand but we’re not getting rain,” said Davenport, who authored a 2019 study on the relationship between flood size and snow or rainfall in the Western U.S.
More winter rainfall, she said, means that not only is the summer drier because of a lower snowpack, but more water will flow straight into streams and rivers, raising the chances that they overtop their banks.
California has always been a land of extremes, said Diana Zamora-Reyes, a scientist at the U.S. Geological Survey who studies water and climate change in California. The difference now, she said, is that the state is swinging “from more extreme to more extreme, and there’s no middle anymore.”
Research has found that California’s average annual precipitation may stay largely the same as the planet warms, but that climate change is already making that precipitation fall in shorter, more intense bursts, with longer dry periods.
The intensity of recent rainfall has forced a reckoning among state environmental officials.
“We’ve gotten used to thinking we need to prepare for the worst-case scenario under drought circumstances,” said Yana Garcia, California’s secretary for environmental protection. “These flood events have thrown a wrench into how we’ve thought about what our future would look like.”
A multi-headed threat
There are also surprising public health consequences of climate whiplash.
Valley fever, a potentially deadly fungal disease that lives in soil and spreads in dust, thrives amid extreme swings in rainfall and drought.
The disease, once confined to Arizona and California’s lower San Joaquin Valley, has been spreading across the American West, largely driven, scientists say, by climate change.
Jennifer Head, an epidemiologist at the University of Michigan who studies Valley fever, said the increasingly dramatic transitions between wet and dry extremes raise the risk of infection.
“Concentrating precipitation into specific periods—wetter winters, drier summers—is the prime conditions for Valley fever to spread,” Head said. “Giving it more moisture during the growth period and more dryness during its transmission period can enhance both of those processes.”
California saw a record 9,280 Valley fever cases in 2023, according to the state’s health department, up nearly 300 percent from 2014. And officials reported more than 5,000 preliminary cases through the first half of this year, putting the state on track for another record high.
In Butte County, Loeser must contend with all these threats daily, while ensuring there’s always enough water to drink, grow crops, and recreate. Groundwater provides some relief during dry years, she said, but that too must be carefully managed to ensure the aquifer doesn’t run dry.
Amid today’s volatile climate, she’s also preparing for a future where wet and dry extremes get even more intense.
“We haven’t had a recent five- or six-year drought,” she said. “That’s when, I think, things will really get interesting.”
