Santa Ana winds

Based on Wikipedia: Santa Ana winds

The Devil's Breath

In January 2025, winds gusting at over eighty miles per hour—speeds comparable to a Category 1 hurricane—tore through Los Angeles, driving walls of flame that killed at least twenty-four people and consumed more than thirty-five thousand acres. The Eaton Fire and Palisades Fire weren't anomalies. They were the latest chapter in a story that's been repeating for at least five thousand years.

The Santa Ana winds.

Locals sometimes call them the devil winds, and you'd be forgiven for thinking the name fits. These are winds that make autumn in Southern California hotter than summer. Winds that can drop relative humidity below ten percent—drier than the Sahara Desert. Winds that turn the region's native chaparral into explosive kindling, then provide the oxygen to make it burn.

But here's what makes the Santa Anas genuinely strange: they blow the wrong way. Along most coastlines around the world, winds come from the sea during the day, drawn inland as the land heats up faster than the water. The Santa Anas reverse this logic entirely. They come roaring down from the mountains, pushing outward toward the Pacific Ocean with such force that they sometimes prevent the normal sea breeze from forming at all.

How Mountains Make Wind

To understand the Santa Anas, you need to picture the geography of Southern California. Imagine a bathtub. The Pacific Ocean forms one wall. The Transverse Ranges—mountains that run east-west, unusual for California—form another. And behind those mountains sits an enormous, elevated bowl called the Great Basin, stretching across Nevada and into Utah.

The Great Basin is high desert, ranging from four thousand to over fourteen thousand feet in elevation. It's cold up there, especially in autumn and winter. Cold air is dense, and dense air creates high pressure. Meanwhile, off the California coast, the Pacific often harbors areas of low pressure.

Physics takes over from here. Air flows from high pressure to low pressure, the way water flows downhill. But the Transverse Ranges stand in the way—peaks rising to ten thousand feet and higher. The air can't go through the mountains, so it takes the path of least resistance: mountain passes.

Three passes matter most. The Soledad Pass connects the Mojave Desert to the Santa Clarita Valley. The Cajon Pass funnels wind toward San Bernardino and Fontana. The San Gorgonio Pass channels air toward Palm Springs and the Coachella Valley.

These passes act like nozzles on a garden hose. As the rushing air gets squeezed through narrow gaps, it accelerates dramatically—a phenomenon physicists call the Venturi effect. Winds that might be twenty miles per hour in the desert can hit gale force or stronger by the time they exit these mountain corridors.

The Paradox of Heating

Here's something counterintuitive: the Santa Ana winds start cold but arrive hot.

The air masses that create these winds often originate over Canada, pushing south as frigid Arctic air. By the time this air settles over the Great Basin, it's chilled by the high elevation. So how does cold air become the scorching winds that make October in Malibu hotter than July?

The answer involves a piece of physics called adiabatic heating. When air descends from high elevation to low elevation, the increasing atmospheric pressure compresses it. Compression heats gases—this is why a bicycle pump gets warm when you use it. For every thousand feet the Santa Ana winds descend, they warm by about five degrees Fahrenheit.

The Great Basin sits roughly four to six thousand feet higher than the Los Angeles coastal plain. That's a twenty to thirty degree temperature increase just from the descent, on top of whatever warming occurs as the air passes over sun-baked desert landscapes.

The humidity drops just as dramatically. Relative humidity is inversely related to temperature—warm air can hold more moisture, so the same absolute amount of water vapor represents a smaller percentage of the air's capacity. Air that was merely dry in Nevada becomes desperately, dangerously dry by the time it reaches the coast.

Not a Föhn, But Something Similar

Meteorologists are particular about categories, and they draw a distinction between the Santa Anas and another famous mountain wind: the Föhn.

The original Föhn blows in the Alps, and the Chinook—its North American cousin—sweeps down the eastern slopes of the Rocky Mountains into Alberta and Montana. These winds work differently. They start as moist air that rises up the windward side of a mountain range, dropping rain or snow as they climb. That precipitation releases latent heat—energy that was stored when water originally evaporated into the atmosphere. So by the time Föhn winds descend the other side, they've been pre-warmed by this moisture release.

Santa Anas skip this step. The air that feeds them has already lost its moisture far upwind, often through a different process called subsidence—descending from high in the atmosphere where it was cold and dry to begin with. There's no latent heat boost. Just raw physics: compression and acceleration.

The distinction matters because it affects how these winds behave. Föhn winds can bring clouds and even occasional precipitation. Santa Anas almost never do. They bring only heat, aridity, and crystalline visibility—skies so clear you can see islands sixty miles offshore.

The Fire Calendar

Southern California has two fire seasons, and understanding them requires understanding two different kinds of wind.

Summer fires tend to be driven by simple heat. Long days, minimal rainfall, dried-out vegetation. These fires can grow large, but they often move slowly, pushed by ordinary sea breezes or terrain effects. Firefighters have time to respond, establish containment lines, and protect structures.

Santa Ana fires are different. They explode.

The combination is lethal: vegetation that's spent a long dry summer turning into fuel, humidity so low that plants essentially become kindling, and winds strong enough to carry embers more than a mile ahead of the fire front. A fire that might take days to spread in normal conditions can cross thousands of acres in hours during a Santa Ana event.

Forecasters use a simple rule of thumb. They measure the pressure difference between Los Angeles International Airport and Las Vegas. When that difference reaches nine millibars—about a quarter inch of mercury on an old-fashioned barometer—conditions favor a Santa Ana event. But the most intense Santa Anas coincide with Arctic air masses plunging south from Canada. Counterintuitively, the coldest source air produces the hottest, most dangerous winds.

A Catalog of Destruction

The fires keep coming. They've been coming for millennia, long before European settlement.

The Tongva and Tataviam peoples, who inhabited the Los Angeles Basin for thousands of years, lived with these winds and the fires they brought. Some anthropologists believe these indigenous communities used controlled burns to manage the chaparral, working with rather than against the fire ecology.

European settlers brought a different approach: suppression. They also brought denser development, more people, more structures in the path of flames. The result has been an escalating cycle of destruction.

The 1889 Santiago Canyon Fire. The 1961 Bel Air Fire, which destroyed nearly five hundred homes in one of Los Angeles's wealthiest neighborhoods. The 2003 Cedar Fire in San Diego County, which killed fifteen people and burned over 273,000 acres. The 2007 Witch Creek Fire. The 2017 Thomas Fire, which became, at the time, the largest fire in modern California history.

And then January 2025.

The wind event that drove the Palisades and Eaton fires lasted twenty-four days, from January 6th through January 31st. The Santa Anas came and went in waves, allowing firefighters to make progress before gusts would return and send flames racing in new directions. Twenty-four people died. Entire neighborhoods that had stood for decades simply ceased to exist.

The Strongest Ever Recorded

In early December 2011, the atmospheric dice came up in a particularly cruel configuration.

Pasadena and Altadena, cities tucked against the base of the San Gabriel Mountains, experienced sustained winds of ninety-seven miles per hour. That's not gusts—that's sustained, ongoing wind speed, maintained minute after minute.

The gusts were worse. Instruments recorded 167 miles per hour before several weather stations simply stopped functioning. For context, a Category 5 hurricane—the strongest classification—requires sustained winds of 157 miles per hour or more. The December 2011 Santa Ana gusts exceeded that threshold.

Trees toppled. Power lines snapped. Roofs peeled off buildings. Remarkably, no major fires started during this particular event—a testament to both luck and the fact that December vegetation isn't quite as dry as what you find in October or November.

The Ocean Responds

The Santa Anas' influence extends beyond the land.

As these powerful offshore winds blow across the Pacific's surface, they push the warm upper layer of ocean water away from the coast. Cold water rises from the depths to replace it—a process called upwelling. Surface temperatures can drop seven degrees Fahrenheit or more within a day or two of a strong Santa Ana event.

This cold, deep water brings nutrients with it: phosphates, nitrates, the building blocks of marine food chains. Phytoplankton bloom. Fish populations that depend on these tiny plants thrive. The Santa Ana winds, for all their destructive potential on land, essentially fertilize the ocean.

But the winds also create hazards at sea. The Channel Islands—Catalina, Santa Cruz, Anacapa, and others—normally have their sheltered harbors on the north and east sides, facing away from the prevailing westerly winds. Santa Anas flip this logic. Suddenly the typically calm anchorages at Avalon and Two Harbors are exposed to driving winds and building seas. Boats tear loose from moorings. Inexperienced sailors find themselves in trouble.

During strong Santa Ana conditions, the Coast Guard advises vessels to either moor on the southern, windward side of the islands—normally the exposed side—or return to the mainland entirely.

The Fog That Follows

When Santa Ana conditions finally break, something strange can happen.

Picture the scene: days of hot, dry, windy weather. The marine layer—that cool, moist blanket of air that normally hugs the Southern California coast—has been completely displaced. The Pacific Ocean's surface has been exposed to dry desert air for days.

Then the high pressure system weakens. The wind dies. And if conditions align properly, the marine layer reforms with startling speed. Moisture that evaporated from the ocean over days reconcentrates into a dense fog bank in hours.

If the wind gradients reverse—shifting from offshore to onshore—this wall of fog can sweep into coastal cities in as little as fifteen minutes. One moment, clear skies and hot temperatures. The next, you can't see across the street, and the temperature has dropped twenty degrees. Meteorologists call this Santa Ana fog, and while it's rare—requiring a specific sequence of conditions—it's one of the more dramatic weather transitions you can experience in North America.

More often, the high pressure simply lingers after the wind stops. Days or even weeks of warm, dry, stagnant conditions follow the wind event, a kind of atmospheric hangover.

Valley Fever Rides the Wind

There's another danger in Santa Ana winds that most people never consider.

In the desert soils of California's Central Valley and southwestern states lives a fungus called Coccidioides. It spends most of its life cycle as delicate filaments in the dirt, harmless and invisible. But when the soil dries out and the wind picks up, those filaments fragment into tiny spores—small enough to float on air currents, small enough to lodge deep in human lungs.

Doctors call the resulting infection Valley Fever, and it's far more common than most people realize. In years with strong Santa Ana winds, emergency rooms throughout Southern California see spikes in cases. About forty percent of people who inhale the spores develop symptoms: fever, cough, fatigue, rash. Most recover on their own. But a small percentage develop serious pneumonia, and an even smaller number see the infection spread throughout their bodies—to skin, bones, the lining of the brain.

Disseminated coccidioidomycosis can be fatal. It's particularly dangerous for people with compromised immune systems, pregnant women, and certain ethnic groups—Filipino and African American populations seem to face higher risks, for reasons that remain unclear.

The Santa Anas carry these spores from endemic areas into cities where the fungus doesn't normally grow. People in Los Angeles or San Diego can develop Valley Fever from winds that passed through Kern County or the Antelope Valley hundreds of miles away.

What's In a Name?

The etymology of "Santa Ana winds" has been contentiously disputed for over a century, which tells you something about California boosterism and the lengths to which chambers of commerce will go.

The straightforward explanation is that the winds get their name from Santa Ana Canyon in Orange County—one of the many mountain gaps through which the winds funnel toward the coast. The canyon, in turn, was named for the Santa Ana River, which was itself named because the Portolá expedition—Spanish explorers mapping California in 1769—entered the river valley on the feast day of Saint Anne, July 26th.

Newspaper references to "Santa Ana winds" appear as early as 1871, when the Anaheim Gazette used the term. For locals at the time, the name was simply descriptive: the winds seemed to come out of Santa Ana Canyon, so that's what they called them.

But the city of Santa Ana had a problem with this.

By the early 1900s, Southern California was aggressively promoting itself to potential migrants from the East Coast and Midwest. The last thing civic boosters wanted was their city's name associated with destructive, uncomfortable weather. When a sensationalized 1901 wire story about wind damage spread the term "Santa Ana winds" nationally, the Santa Ana Chamber of Commerce launched what can only be called a misinformation campaign.

They claimed the name was actually "Santana winds"—supposedly derived from a Native American phrase meaning "big wind" or "devil wind," which Spanish speakers then corrupted into something that sounded like their word for Satan: Satanás. Over time, this story went, English speakers further corrupted it to "Santa Ana."

It's a colorful story. It's also completely fabricated.

Linguists who study the Gabrielino and Juaneño languages spoken by the region's indigenous peoples have found no evidence of any word resembling "Santana" or "sandana." The supposed Native American origin was invented by early twentieth-century boosters hoping to distance their city from bad weather publicity.

Another folk etymology connects the name to General Antonio López de Santa Anna, the Mexican military leader who fought at the Alamo. This explanation suggests the winds were named for dust clouds kicked up by cavalry horses. It's creative, but there's no historical evidence for it, and the timeline doesn't match—Santa Anna's military campaigns were in Texas, not California, and occurred decades before the first recorded uses of the term.

The Santa Ana Journal, the city's local paper, fought for years to discourage the association. In 1935, they published a verse alongside a story about wind damage that nodded to the "devil winds" folklore: "The devil sends the naughty winds / To blow the skirts on high; / But God is just and sends the dust / To fill the bad man's eye."

The campaign failed. More than a century later, we still call them the Santa Ana winds.

The Sundowners

About a hundred miles up the coast from Los Angeles, in the Santa Barbara and Goleta area, a related phenomenon goes by a different name: the sundowner winds.

Sundowners share the same basic mechanism as Santa Anas—high pressure over the interior pushing air down through mountain passes toward the coast. But their timing differs. They occur most frequently in late spring and early summer rather than autumn, and they're strongest right around sunset, hence the name.

Because high pressure systems typically migrate eastward across the continent, sundowner events often precede Santa Ana events by a day or two. When forecasters see sundowner conditions developing in Santa Barbara, they start preparing for Santa Ana conditions in Los Angeles and Orange County.

The 2008 Tea Fire, which destroyed over two hundred homes in Montecito and Santa Barbara, was driven by sundowner winds. The 2017 Thomas Fire, which started in Ventura County but eventually burned into Santa Barbara County, experienced both Santa Ana and sundowner conditions during its month-long rampage.

Living With the Devil

The fundamental reality is that the Santa Ana winds aren't going away. They're as much a part of Southern California's climate as sunshine and drought.

The region typically experiences ten to twenty-five Santa Ana events per year. Each event lasts an average of three days, though they can persist for a week or more. The longest recorded Santa Ana—fourteen straight days of offshore winds—occurred in November 1957.

Climate change is complicating predictions. Some models suggest the frequency of Santa Ana events may decrease as the planet warms—changes in atmospheric circulation patterns could weaken the high pressure systems that drive the winds. But other research indicates that when Santa Anas do occur, they may be more intense, lasting longer and bringing even lower humidity.

Meanwhile, development continues to push into the wildland-urban interface—those dangerous zones where houses meet chaparral. More than eleven million people now live in Southern California's fire-prone regions, and that number grows every year.

The Tongva knew these winds for thousands of years before the first European ship appeared on the horizon. They knew that fire was part of the landscape, as inevitable as rain in other climates. Whether modern Californians can develop that same acceptance—and the adaptations that come with it—remains an open question.

The devil winds will keep blowing either way.