Santa Ana winds are strong, dry downslope winds that originate in the Great Basin and descend through mountain passes and canyons in Southern California. They commonly occur during the fall and winter months when high pressure over the Great Basin and low pressure over Southern California create a pressure gradient that forces air to flow from the northeast toward the southwest.

Here are some key characteristics of Santa Ana winds:

Strong Winds: Santa Ana winds are known for their strength. Wind speeds can range from 20 to 50 miles per hour (32 to 81 kilometers per hour) but can sometimes exceed 80 miles per hour (129 kilometers per hour).

Downslope Winds: As the air descends from the mountains, it warms and dries due to compression (adiabatic compression). This process contributes to the low humidity levels associated with Santa Ana winds.

Dry Conditions: Santa Ana winds transport air from the interior deserts, resulting in low humidity levels in Southern California. Relative humidity can drop below 10%, creating extremely dry conditions that increase evaporative demand on vegetation and raise the risk of wildfires.

Seasonal Occurrence: Santa Ana winds predominantly occur during the fall (September to November) and winter (December to February), although they can also occur less frequently during spring and summer.

Weather Impact: Santa Ana winds can significantly impact the weather in Southern California. They tend to clear skies, raise daytime temperatures, reduce nighttime temperatures, and contribute to hot and dry conditions.

Wildfire Risk: The combination of strong winds, low humidity, and dry vegetation greatly increases the risk of wildfires. Historical wildfires such as the Laguna Fire (1993), Santiago Canyon Fire (2007), and the Witch Creek Fire (2021) were exacerbated by Santa Ana wind conditions.

Due to their potential hazardous impacts, Santa Ana winds are closely monitored and forecasted by the National Weather Service. When these winds are expected, advisories or warnings are issued to alert the public and emergency services to take necessary precautions.