This is a Santa Ana.

This is a Santa Ana wind, aka Devil Winds, or more generally as katabatic winds. (ref: https://en.wikipedia.org/wiki/Santa_Ana_winds )

This is why one of my primary life goals is to leave Southern California forever.

Santa Ana winds are a weather pattern found in Southern California. They are characterized by extremely low humidity and strong winds coming from the east. They are most common around October and November, but they can happen at any time of year. Between the heat, dryness, and winds, they are the principal drivers behind SoCal's fire season.

As you can see from the graph, we are experiencing one right now. Over the course of a mere ~18 hours, the dewpoint (a measure of absolute humidity) drops 50 degrees F. This turns otherwise-pleasant fall weather into a nightmare of dry eyes, nosebleeds, burning lungs, and buckets of moisturizer. As weather patterns go, it might not kill you, but it will make you wish it did.

Physically, these winds arise when high pressure builds over the Great Basin (~Utah and Nevada). The high pressure pulls air in a counterclockwise direction around it, pushing it high over the Rocky Mountains and the Sierra Nevadas. As the air gets so high, it gets very cold; and as air gets colder, it can't hold as much moisture, so it precipitates out - essentially freeze drying it.

Then the air continues its route until it falls down the mountain slopes east of the populous areas of Southern California. As it falls, it converts its potential energy from being very high up into kinetic energy by picking up speed and thermal energy by getting much warmer - but the humidity stays very, very low. To make it worse, it picks up sand and dust from the deserts, further ruining the air quality.

If anyone you know is even slightly considering moving to California, show them this first. We might have a reputation for being sunny all the time, but everyone should know that is actually a BAD thing. Very, very, VERY bad.