You hear about them during the sweltering summer months, when plant life dries up and the smallest spark can lead to catastrophe. When Los Angeles and the surrounding areas are on high alert for potential wildfires, they have the potential to wreak havoc. They’re called Santa Ana winds.

Coastal Southern California’s one-of-a-kind geography – mountains on one side, the Pacific Ocean on the other – gives those who live there breathtaking views and a lifestyle that is as unique as the region’s topography itself.

But the distinctive terrain also gives rise to its own set of meteorological phenomena that can create major challenges for the people who call the area home, particularly during wildfire season. Arguably no regularly occurring weather is more notorious for this than Santa Anas.

The National Weather Service keeps a constant eye on the conditions that allow for Santa Ana winds to make an unwanted appearance during fire season. And while the pesky winds are well understood by weather forecasters and meteorologists, the average person might have their own questions about Santa Ana winds and the issues they create during fire season.

Meteorologist Ryan Kittel with the NWS Los Angeles/Oxnard spoke to KTLA and answered questions about Santa Ana winds and what to expect as wildfire season approaches.

Kittle’s responses are below and have been edited for clarity.

Q: What exactly are Santa Ana winds and why do they happen?

A: Santa Ana winds are gusty winds that blow in the opposite direction (east to west, sometimes called “offshore” winds) of the typical wind we see in southern California (west to east, also called the seabreeze or “onshore” winds). They form when cold, dense air forms to our north and east (usually over the Great Basin around Nevada and Utah), usually due to a cold weather system that passes through the western United States. 

That dense air wants to spread out in all directions, including toward southern California. Since the area to our east is typically dry (deserts), Santa Ana winds blow dry desert air into the coastal areas instead of moist ocean air associated with the typical onshore winds. Since places to the east are associated with higher elevations than the coast, that air will compress (higher pressure at lower elevations, similar to what we experience when landing on an airplane or driving down a mountain). When the air compresses, it warms. As a result, Santa Ana winds are often associated with warm, dry, and windy conditions.  

Q: How can you predict when Santa Ana winds will appear? What are the signs of an upcoming wind event?

A: The mechanisms of what causes Santa Anas are well understood. Since they are usually caused by a cold weather system moving through the western U.S., keeping an eye out for such systems is the first step. With the continued advancement of computer projections, we are able to predict those systems and the resulting Santa Anas well in advance – often one week out and sometimes two weeks out. We also have a growing network of automated weather stations to help detect the winds as soon as they start. We also have continually advancing satellite systems that even help us detect when a fire breaks out. 

Q: Are Santa Ana winds specific to the Los Angeles area? Do other regions in California have their own wind phenomena?

A: Santa Ana winds are specific to our area, but there are similar winds in other areas with different names. Winds like the Santa Anas are generically called foehn winds, which is any kind of warm and dry wind that moves down a mountain side. Foehn winds affect parts of Colorado, Germany, Australia, and Chile.  

Q: Why are Santa Ana winds so dangerous during fire season? What challenges do they present for firefighters?

A: For a fire to grow really fast, it needs dry plants (fuel) to burn and strong winds to drive burning embers onto unburned fuels downwind. Santa Ana winds are often strong enough, and being warm and dry, will dry out many of the fuels quickly. It really provides the perfect environment for a fire. Fortunately the National Weather Service is pretty good at predicting these wind events several days out. Because of our good relationships and partnerships with many fire agencies, we are able to keep them aware of any Santa Ana events coming up. This allows them to have extra firefighters on duty before an event starts, so they can provide a strong initial attack if any fire were to break out. Some events are so strong however, that a fire can become so large, so quickly that even the best preparation cannot stop it.   

Q: What is a ‘Red Flag’ warning? How should residents prepare for Santa Ana wind events?

A: Red Flag Warnings are issued by the National Weather Service when the environment is favorable to rapid fire growth and extreme fire behavior. It does not mean that a large fire will happen, but it does mean that if a fire were to start, it could easily and quickly become large and dangerous. We issue Red Flag Warnings when the winds are expected to be strong, the air is very dry, and the fuels are very dry. These warnings allow fire agencies to more easily pre-position and deploy resources in case a fire starts. 

These warnings should also alert the public to be extra cautious with anything that could start a fire (like fireworks, campfires, cigarettes, and even dragging tow chains and industrial weed wackers). These warnings should also alert any residents in high fire risk areas, like those living near forest boundaries, to be set to evacuate if a fire starts near them. Those residents can visit readyforwildfire.org for more information, including the Ready, Set, Go program.

Q: Are Santa Ana winds affected by global climate change?

A: There is growing evidence that climate change is one of the ingredients for a generally growing threat for wildfires in Southern California. 

As high wildfire season approaches in Southern California, Santa Ana winds will likely play a critical role in how fires will behave and how firefighters will strategize how to battle each blaze and keep homes and lives protected.

Kittel and the rest of the National Weather Service will keep everyone informed along the way.