The Hollywood sign towers over Los Angeles, watching its embers dance like wayward stars on a January night. Fiery debris drifts through multimillion-dollar mansions on warm winds while emergency crews battle a fire that shouldn't exist — not in winter, not here, not now.
Two thousand miles east, in America's heartland, a different emergency is playing out. The mercury plummeted to depths not seen in a decade. Wind chills reach below 40 degrees. Airlines have hundreds of ground flights. The roads turned into dangerous swaths of ice. People huddled in the warming center while polar winds howled outside like hungry ghosts.
Fire and ice. A country is divided into two.
We've been here before. The first dramatic chapter of this story was written in the winter of 2013-14. California is experiencing its worst drought in 1,200 years, so severe that the fruit basket in the United States is withering. At the same time, the eastern United States is experiencing what the media calls a "polar vortex return." The temperature swings between California and the East Coast that winter were unlike anything we've seen in modern records.
That winter changed the way we think about climate. At Utah State University, our research Revealed something fascinating: The atmosphere behaves like a river meeting a boulder. Just as water creates waves when it goes around obstacles, our atmosphere creates waves when it encounters mountains and ocean heating patterns. These aren't just any waves - they're huge atmospheric ripples that can span continents.
Think of the jet stream (the current of air flowing high above our heads) as a cosmic garden hose. When it's straight, it keeps weather patterns changing normally. But recently, something has made it more drastic. early research The culprit was found: significant warming in the western Pacific, creating an atmospheric domino effect that stretched all the way to North America.
Here's how it works: The warm western Pacific acts like a hot plate beneath the atmosphere, creating rising air that sends waves eastward, like throwing a stone into a pond. These waves travel along jet streams—these cosmic highways of atmospheric disturbances. When these waves reach North America, they can get "stuck" in a specific pattern that creates persistent extreme weather on both coasts or on one coast and the Midwest.
By 2017, we saw another manifestation of this pattern, but with a twist. Big swings in California From drought to flood Atmospheric rivers—rivers of water vapor in the sky—lashed the state. Then in January 2018, the eastern United States succumbed to severe cold again, while the West remained stubbornly warm and dry. This pattern becomes more pronounced and more persistent.
The evidence for this amplification is more than anecdotal. our research The intensity of these winter extremes has increased by about 20% since the late 20th century. We can literally see the shape of its jets, which now often twist into deeper waves than they did just a few decades ago. Like a river that once flowed straight begins to become more meandering.
The physics behind this are clear. Western Pacific warming is not a random fluctuation; This is part of a larger climate change pattern. This warming creates stronger "wave trains" of atmospheric energy that travel along the jet stream and into North America. When these waves interact with our mountains and existing weather patterns, they create this persistent seesaw effect from coast to coast.
Now, in 2025, we will see the same pattern play out again, but with greater intensity. The Palisades Fire has become the most destructive winter fire in Los Angeles history, while the eastern United States faces its worst winter storm in a decade. This is no coincidence. This is the same atmospheric pattern we've been tracking for years, flexing its power like never before.
The changes we see are no longer subtle. Our latest research A specific atmospheric fingerprint that is becoming increasingly frequent and intense across the western United States has been identified. It's a unique three-part wave in the atmosphere that creates perfect conditions for fires, and has been occurring more frequently since 1980 due to subtropical warming in the eastern Pacific.
This pattern is called a weather regime, and it has some potential effects on the landscape: It greatly increases the atmosphere's thirst for moisture. When this weather pattern occurs, it's not just a lack of precipitation that exacerbates drought: the atmosphere itself sucks moisture from soil, vegetation, and everything else, turning California's landscape into a tinderbox. pattern Fires can last for weeks, igniting fires even during the wettest, coldest seasons of the year.
What’s particularly concerning is how this pattern is self-reinforcing. As the terrain dries, it heats up more easily, strengthening the atmospheric ridges that caused the drying in the first place. It's a vicious cycle that could turn winter into an extension of fire season. In 2014, the pattern was so strong that NASA satellites could see California's mountains rising as the weight of water disappeared from the surface.
But understanding these patterns gives us power. In 2014, we were caught off guard. By 2017, we were better prepared, although the intensity still surprised us. Now, with 5 million Californians under red flag warnings and 60 million Easterners facing winter storm warnings, we can at least see it coming. Forecasters can warn communities days in advance. Emergency managers can deploy resources before they are needed. Communities can prepare.
The question is not whether these patterns will persist; Our research shows they will. The question is how we will write the next chapter, how we will adapt to this new normal, in which there is no calendar for fire season and our atmospheric patterns are being redrawn by a warming world.
Robert Frost once pondered whether the world would end in fire or ice. This winter, America doesn’t have to make a choice. Understanding new patterns in climate doesn't make them any less compelling, but it does give us a fighting chance to prepare for what's coming next.
Shih-Yu Simon Wang is a professor of climate science at Utah State University.