Water Vapor in the Air Think about why the bathroom mirror and windows fog up during a hot shower. During a hot shower, some of the hot water spraying from the shower evaporates into the air. The water content of the air, humidity increases. Some of the water vapor that touches the mirror condenses because the mirror's surface is cooler than the humid air. The water condenses out of the air and forms drops of liquid water or dew on the mirror.
Humidity is the amount of moisture in the air at a certain temperature.
At higher temperatures air can hold more humidity. Relative humidity means how much water is in the air compared to the maximum amount that could be there at the same temperature. Los Angeles's air will have more moisture because the air is warmer. We feel more uncomfortable when it is hot and humid, because it takes longer for our perspiration to evaporate, since the air is at near capacity of water vapor. Perspiration evaporating from our skin cools us because of latent heat.