Humidity describes the amount of water vapor in the
air. Warm air can hold more water vapor than cold water. Tropical areas
are noted for their high relative humidity. On a humid day, people with
naturally curly hair experience the "frizzies" caused by a
stretching of the hair.
Clouds, fog, and dew are formed when
condensation occurs. The air must be saturated with water vapor and tiny
bits of particulate matter known as condensation nuclei must be present.
These nuclei serve as surfaces for the condensation of water vapor.
In cloud formation the process is rapid and
results in the formation of billions of tiny water droplet. They are so
fine that they remain suspended in air. Difference in heat within clouds
can cause convection which allows the small droplets to move within the
cloud. This is when it gets interesting. The droplets can freeze as it
gets colder and then in warmer areas, they melt. All these different
conditions cause different types of weather.