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The Los Angeles area is engulfed in some of the worst fires it has experienced in more than a decade, blazes that had killed as many as five people, forced an estimated 80,000 residents to evacuate their homes as of last night, and caused damage to a growing number of businesses and buildings.

The infernos began with the Palisades fire, which started along the Pacific coast near the Santa Monica mountains on Tuesday morning, spreading to more than 15,000 acres along California’s Pacific Coast Highway by Wednesday evening. A second major fire, the Eaton fire, erupted Tuesday night near Pasadena and had razed more than 10,000 acres within 24 hours, according to the Los Angeles Times. Meanwhile, other smaller fires also are burning in the Los Angeles area.

The fires should hardly come as a surprise, writes Vox correspondent Umair Irfan in his latest piece: “Fire forecasters have been warning since the beginning of the year that conditions were ripe for massive infernos, particularly in southern California.” But a host of other factors have also heightened wildfire risk in California and around the world. 

I talked with Umair about why megafires like these are becoming more common, and why California in particular is so susceptible to them. (Our conversation has been condensed for length and lightly edited.)

Lavanya Ramanathan: What factors have made California so susceptible to fires? And they have worsened, right? 

Umair Irfan: The core thing to remember is that wildfire is a natural part of the ecosystem. In California, you naturally will see wildfire at various points throughout the year and in different ecosystems. Seeing things burn is natural. It happens on its own.

There are ways humans are making them more severe and more destructive, and one of the big ones is that the vast majority of fires now are ignited by humans. This is not necessarily arson. We're talking about things like downed power lines, sparks from cars, vehicles, people being careless with fires and matches, barbecue grills, and things like that. 

So the sources of ignition are increasing, and they tend to increase around human activity. And increasingly, people are living closer and closer to wildfire-prone regions; as they get priced out of big cities, they move into more rural areas. There's a lot of sprawl, especially in places like Southern California. 

Then in the background, humans have modified the landscape very drastically in a lot of different ways, in the wooded areas of California, mainly further north. And they have naturally suppressed naturally occurring wildfires. That's led vegetation to accumulate, so when a fire does ignite that we can't avoid, there's a lot more fuel there to burn.

What led to the fires we’re seeing right now?

Around Los Angeles and San Diego, there’s mainly grassland. It's chaparral, the short and fast-growing vegetation that varies year to year. Fast-growing grasses grow a lot when there's a lot of rainfall. And so last winter, around late 2023 and early 2024, California saw an extraordinary amount of rainfall, particularly Southern California. There were record amounts of flooding. 

That led to a bumper crop of these grasses growing. And that was then followed by a summer of record-breaking heat all over California and in Southern California, and so that dried out the vegetation. And then this winter, we saw it start with very limited rainfall. This has been one of the driest winters they've seen on record. 

Turning the plants essentially into tinder. 

Exactly. That's exactly the sequence you see, a wet winter followed by a dry summer, and then a dry winter. 

On top of all that, you have this phenomenon called the Santa Ana winds. In many parts of coastal California, you have seasonal winds. They blow down from the mountains, they pick up speed, they dry out, and they blow toward major cities. And in California and Southern California, they're called the Santa Anas. They typically blow in the wintertime. 

This year, they’ve been especially strong. You know we're talking about gusts up to 100 miles an hour, if not more. So you have this hot, dry air blowing in from the mountains toward the coast, over an area that has lots of fuel that's really prime to ignite. And then you have one of the most densely populated parts of the state, with millions of people living there. That sort of converges altogether to create this disaster. 

Justin Sullivan/Getty Images News

These are not your typical Santa Ana winds. What is making them worse?

One of the big factors is that we see this sort of meandering jet stream. The jet stream is this river of air that typically forms circles around the planet, but when the oceans heat up, it can cause bends in the jet stream. It will push one lobe of it north, it'll push another lobe of it south. And as it forms these bends, it tends to trap air in them, and then that air, as it gets trapped, it sinks and creates an area of high pressure. When that high-pressure air lands over the Great Basin, over some of the mountains that are further inland, it squeezes the air below it, and then pushes them toward the coast.

The past two years have been the hottest years that humans have ever measured. The Pacific Ocean is still above typical temperatures for this time of year. That's helping bend the jet stream and contain these pockets of air over the inland origins of these wind currents, essentially. And scientists were able to anticipate this; there were some forecasts at the beginning of this year basically saying that we’re going to see some pretty strong Santa Ana winds and that the fire risk is extremely high. This is not an unforeseen event. 

Could Angelenos have taken precautions to protect themselves?

They did take some steps. There were a lot of alerts going out, limiting places where people could go, where the wildfire risk is high. Some recreational areas were closed off. A lot of city officials were taking precautions making sure that wildfire-fighting resources were present and that they were staged in areas. They were telling people to be on high alert. But there's only so much you can do when you're facing a force of nature. You certainly can't stop it once it ignites very easily. And so it's mainly about management. It's trying to contain the blaze.

Because, again, this is a natural part of the ecosystem. This is going to happen with or without us. The more you try to keep a lid on it, the more it's going to explode when you take your hand off it. 

Abdullah Guclu/Anadalou via Getty Images

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Vox

Ninety-one norovirus outbreaks were reported to the Centers for Disease Control and Prevention (CDC) during the first week of December (shown in the orange line in the chart below), the latest week for which data is available. That’s more than has been reported in a given week since 2012. You can read more about why an unusual number of Americans are dealing with a gnarly stomach bug right now here.

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Today’s edition was produced and edited by senior editor Lavanya Ramanathan, with contributions from staff editor Melinda Fakuade. We'll see you tomorrow!

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