California’s Extreme Weather: A Cycle of Drought, Deluge, and Wildfire Risk

In the last 15 months, Southern California has experienced a series of extreme weather events – the most destructive wildfires in its history, the wettest holiday season in recent memory, and a record-breaking March heat wave. These seemingly disparate events are connected by a clear through line: climate change, according to UC climate scientist Daniel Swain.

Climate Change and Extreme Weather

“All of the superlative extremes we’ve seen in recent years — from extreme heat to extreme dryness to extreme wetness, and even the severe wildfires — they all have clear links to climate change,” Swain said in an interview. The current heat wave, shattering temperature records across Southern California, is a direct result of a warming atmosphere that intensifies heat-trapping weather patterns, leading to more frequent and severe heat waves.

The recent March heat is notable not only for its intensity but also its duration and scale, extending from Southern California to the Great Plains and from Canada to Mexico. Swain described the event as “extraordinarily extreme.”

From Drought Relief to Potential Drought Return

California briefly achieved a drought-free status in January, thanks to a deluge of winter storms, according to the U.S. Drought Monitor. However, the record-breaking warmth and dryness of March are reversing those gains. Swain warned, “This March is exactly what you wouldn’t wish to notice if you wanted to maintain that drought-free status.” Without significant precipitation, Northern California is on track to reenter drought conditions by spring.

Despite the potential for drought, California’s water infrastructure – its reservoirs – are currently in relatively good shape due to the wet winter. Swain noted that a multi-year drought of significant severity is typically required to seriously threaten the state’s water supply.

The Whiplash Effect: Wet Winters and Dry Falls

A return to drought conditions, however, could still impact California’s agricultural industry and increase wildfire risk. The rapid shift from intense rainfall to extreme heat – a phenomenon Swain calls “hydroclimate whiplash” – is a pattern scientists expect to see more frequently as climate change worsens.

“Sometimes folks will say, well, no, you’ve got to pick one. It can’t be both getting wetter and drier,” Swain explained. “and that’s actually not how the atmosphere operates.” He further clarified that increased rainfall and increased dryness are “two sides of the same thermodynamic coin.” A warmer atmosphere pulls more moisture from soils and plants, exacerbating droughts, although simultaneously holding more water vapor, leading to more intense rainstorms.

Wildfire Risk and the Role of El Niño

This pattern of wet winters followed by dry periods creates conditions ripe for wildfires. Heavy rainfall leads to increased vegetation growth, which then becomes fuel during periods of dryness. While California currently has a low wildfire risk due to recent rains, other Western states are already experiencing early-season wildfires. Swain observed visible wildfire plumes in New Mexico, Arizona, and Colorado in mid-March, calling it “extraordinary” for that time of year.

The upcoming wildfire season in California remains uncertain, particularly with the potential influence of a significant El Niño event. El Niño could bring remnants of a tropical storm, delivering much-needed rainfall and reducing fire risk, as seen with Tropical Storm Hilary in 2023. Conversely, it could also lead to dry-thunderstorm outbreaks with lightning ignitions, similar to what occurred in 2020 with Tropical Storm Fausto.

Swain, a climate scientist with joint appointments at the California Institute for Water Resources within University of California Agriculture and Natural Resources (UCANR) and the Institute of the Environment and Sustainability at UCLA, emphasizes that California, and the United States as a whole, will continue to experience more extreme weather events in the years to come.