The Santa Ana wind is a potentially destructive wind that is set up by a particular weather pattern. The primary destruction is in the form of fires and severe wind. The strong wind and low humidity within a region that is usually very dry all contribute to the potential for major fires. The low humidity is caused by two factors which are wind coming from a dry land source and a downsloping of air. As air travels from a higher to a lower elevation the air will increase in temperature and the relative humidity will decrease. The strong dry wind desiccates vegetation and the land. This helps set up an ideal fire and fire spreading situation. The building of more houses and planting of more trees in the region has increased the threat for forest fires and burning homes. The fires also contribute to air quality problems.

The weather pattern that produces the Santa Ana wind is a high pressure that funnels wind from the dry higher elevation desert areas and into the lower elevation mountain passes and into the major cities of southern California. The mountain passes produce a funneling effect that increases the wind speed. Below is a diagram of the high pressure Santa Ana weather pattern: