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California Flooding: Why Were We So Unprepared? And What Does Climate Change Have to Do with It?

Updated: Mar 1, 2023

Flooded Slusser Road in Windsor California - January 2023.

In the final weeks of 2022, California was hit with one of its stormiest seasons in years. San Francisco, central to the Bay Area, has logged 21.75 inches of rain as compared to its average of 10.75 inches. The storms began to tip off at the end of January, but the month of constant rain was enough to create serious floods and damage all throughout the state.

“The floods are due to recurrent waves of atmospheric rivers that typically lead to very high rainfall,” said Upmanu Lall, an engineering professor and director of the Columbia Water Center.

The category of storm California experienced is known as an Atmospheric River which is a long and narrow, river-like, weather phenomenon that brings substantial downpours. Atmospheric rivers are formed when winds from the Pacific channel weather from the tropics and redirect it to the West Coast. The most well-known air pattern is convection currents where the hot air rises, cools, and then sinks. In this scenario, the humid air from the tropics was redirected toward the Sierra Nevada which was able to hold more moisture due to its higher density. It rose higher in the atmosphere and then cooled bringing the extreme amounts of rain the state experienced this storm season.

“[Atmospheric rivers] are not unusual for California,” said Lall, yet the question that continues to linger in our thoughts, is why were December and January so disastrous?

California is typically known to experience the pattern of El Nino weather which leads to major droughts and a state-wide dry spell, so the rain is crucial to recuperating the ramifications. The rain replenished the land bringing 71% of the population who were dealing with drought down to 46% but in the process, it was responsible for serious damage. California frankly lacks the proper infrastructure to handle the level of storms received and the speed that they traveled, which led to the state enduring 21 (at least) rain-related deaths due to the mudslides and floods that have ensued.

As well, the runoff that washed into different bodies of water, specifically the San Francisco Bay, because in California, there is no good way of storing the water, is remarkable. Instead of saving the water for future droughts—California is a classified desert—the water washed into the sea along with garbage and pollutants that damage waterways. The issue is expansive and has highlighted the necessity for proper flood procedures.

Ultimately, the repercussions were disproportionately devastating because of unsuccessful interactions between state officials and meteorologists who have been predicting sizable rain for weeks. No one expected them to turn out as bad as they were so few did anything. Roads suffered potholes, riverbeds overflowed, and countless houses were flooded because of a lack of action from the state government, a result of simple miscommunication.

“We could have done better given the forecast information we had available. But without the translation into action, the potential value of ‘skillful’ forecasts goes untapped or under-utilized,” said Andrew Ruszkiewicz, a senior staff associate at the Columbia Climate School’s International Research Institute for Climate and Society.

Because of the changing climate, the situation is only growing worse—and California is not the only state suffering. According to the National Oceanic and Atmospheric Administration, the U.S. experienced 18-billion-dollar climate and weather disasters in 2022, resulting in the loss of 474 lives. Last year marked the eighth consecutive year in which the country experienced 10 or more climate and weather events with losses exceeding $1 billion.

It seems like a blanket statement to make but global warming is an issue, and it does affect the strength of the storms. Statistics from the Center for Climate Sciences at NASA’s Jet Propulsion Laboratory say that with every 1.8 degF (1 degC) increase in sea surface temperatures, the number of extreme storms has risen by about 21%. If climate model projections hold true, extreme storms may increase by 60% by the century’s end. With every degree the temperature increases, the air can hold 7% more water so, when those hot tropic winds reach the Sierras, they are significantly fuller of water than they used to be.

Image from space of the movement of an atmospheric river, similar to the orientation of the one that hit California in early 2023.

Unfortunately, California is predicted to continue to see a rise in storms because the climate crisis has yet to be mitigated but the hope is that because of the severity of recent effects, officials will be making stronger efforts to support local communities against the damage.

Along with the atmospheric river that hit the Bay Area came a record snowpack in the Sierra Nevada Mountain Range. According to the California Data Exchange Center, the snowpack levels have reached 223% of their historical average—a record volume since 1995. But even though this snowpack could alleviate some of the stress of California’s drought, it is a drop in the bucket compared to what California needs. The threat of spring rains melting the snow, combined with climate change-driven altitude increase at which snow falls, prevents the snowpack from making a long-term impact.

Snowpack is vital for California’s water supply. The melting of snow throughout the spring and summer creates a gradual release of freshwater that California relies upon to help fill reservoirs. Millions of people rely upon the snowpack for drinking water, power, and irrigation.

Warming global temperatures mean that snow will begin to fall at higher altitudes. A recent study conducted by the University of California Davis on changing winters in the Sierras predicts that if we continue at our current carbon emission rates, rainfall will occur at up to 7,300 ft in elevation by 2050. This means that rain will be more likely to fall throughout most of Tahoe which sits at roughly 6,224 feet. The National Oceanic and Atmospheric Association also predicts that in coastal mountain ranges in the U.S., like the Sierra Nevadas, only one degree of warming will likely dramatically reduce the number of days spent below freezing and cause earlier spring snowmelt. California’s water supply will be deeply impacted by warming global temperatures.

The recent atmospheric river has served to highlight the impacts of climate change on California and given us a glimpse at what the future could look like with warming temperatures. Climate change will continue to create more atmospheric rivers that cause flooding and mass destruction throughout California. These floods will disproportionately impact low-income Californians and marginalized communities without flood insurance. Warming temperatures will continue to worsen our weather and decrease the amount of snowpack we receive. However, the good news is we still have a sliver of time to reverse the effects before they magnify, this requires maintaining courage, working together, and harnessing your passions for action and solutions.


“How Climate Change Is Shaping California’S Winter Storms.” Nytimes.Com, 2023, Accessed Feb. 23, 2023.

Fecht, Sarah. "Flooding In California: What Went Wrong, And What Comes Next". State Of The Planet, 2023, Accessed Feb. 23, 2023.

Clynes, T. (2023) What has California's flooding (and drought) got to do with climate change?, Environmental Defense Fund. Accessed Feb. 23, 2023.

Image Sources:


"Flooded Slusser Road in Windsor California - January 2023 - Sarah Stierch 02" by Missvain is licensed under CC BY 4.0. To view a copy of this license, visit


"Atmospheric River Soaks California" by NOAASatellites is marked with Public Domain Mark 1.0. To view the terms, visit

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