What is a Santa Ana windstorm and how is it fuelling the California wildfires?

ITV News Weather Presenter Alex Beresford explains what factors are behind the wildfires seen in California.

A state of emergency has been declared in Los Angeles in an effort to deal with several wildfires that have torn through multiple neighbourhoods, killing at least two people and forcing tens of thousands to abandon their homes.

All fires - in San Fernando, Altadena, and Pacific Palisades - are currently at 0% containment and have burned acres of land, officials have said, as conditions are expected to worsen.

The causes of the fires are still being investigated, according to the US Forest Service, but officials already have a good idea about what is fuelling them: the so-called Santa Ana winds.

Here, ITV News explains what this weather phenomenon is, and how it is whipping up the California wildfires.

The fierce winds are created by high pressure over the Great Basin - the vast desert interior of the west Credit: AP

What are Santa Ana winds?

The Santa Anas are extreme, dry winds that are common in LA in colder winter months.

The gusty northeast winds usually blow from the interior of Southern California toward the coast and offshore, moving in the opposite direction of the normal onshore flow that carries moist air from the Pacific into the region.

Santa Anas are linked to some of the worst wildfires in the history of Southern California, including the 2023 Cedar Wildfires in San Diego, which burned 273,246 acres of land and killed 15 people.

How do they form?

The winds, which have already topped 80mph this week, are created by high pressure over the Great Basin - the vast desert interior of the West overlapping several states.

The sinking air loses its moisture and flows in a clockwise direction toward Southern California, where it must get past towering mountain ranges that separate the desert from the metropolitan region lining the coast.

Like a slow-moving river that suddenly narrows and turns into rapids, the air speeds up as it squeezes through mountain passes and canyons, becoming drier and warmer as it descends.

A firefighter battles the Palisades Fire in Los Angeles, on January 7, 2025. Credit: AP

The lack of humidity in the air also means it parches vegetation, making it more prone to burning once a fire has started.

Last summer was particularly hot in Southern California, followed by an unusually dry wet season.

California Governor Gavin Newsom said this time of year "traditionally has not been fire season" but it has now become "year-round in the state of California".

LA Country fire officials have described the winds as “tornado-like” and said they were complicating their battles.

Can the winds affect your health?

The Santa Ana winds have the potential to create life-threatening weather conditions. They can lift embers from an existing fire into an unburned area, where they may ignite a new fire.

On Wednesday, local officials said at least two people had died as a result of the fires.

The extreme lack of moisture can also dry out lips, noses, throats and skin.

A man watches as flames from the Palisades Fire close in on his property on January 7, 2025. Credit: AP

How long will it last?

The National Weather Service has said the widespread windstorm is expected to continue into Wednesday, suggesting the strongest wind gusts could reach up to 80 mph and even 100 mph in the mountains and foothills.

The expansion of wildfire is not likely to get better soon, Los Angeles Mayor Karen Bass said on Wednesday morning.

“Angelenos should be advised that the windstorm is expected to worsen through the morning and to heed local warnings, stay vigilant and stay safe,” Bass posted to her X account.

How are they impacting the California fires ?

ITV News Weather Presenter Alex Beresford says: ‘The infamous Santa Ana winds are driving the fires out of control.

"California often falls victim to wildfires due to its warm climate even in winter like today, the landscape and the raging Santa Ana winds which shoot up the Santa Monica mountains on the northeast side and rush down the other into California much drier and warmer.

"They move in the opposite direction to onshore winds which naturally carry more moisture off the sea. This creates a very dry environment for wildfires to spread quickly."

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