Re: How does humidity affect the formation of rain/snow (precipitation)?

You have a lot of pieces to the puzzle of cloud and precipitation formation already...with a little more information you should be able to put them all together.

Clouds are formed when molecules of water vapor condense into water droplets. Condensation occurs when the atmosphere becomes saturated, that is, when the relative humidity reaches 100 percent. Saturation occurs when airs is moistened and/or lifted and cooled to its dewpoint temperature. In other words...moisture can be transported to a region, say from the ocean to inland areas, raising the dewpoint of the airmass. Or the air itself can be lifted by some mechanism, say heating of the underlying surface or pushed up by an invading cold front. As the air rises, its temperature cools. Lifted high enough, the air will cool to its dewpoint temperature.

What kinds of clouds form depends on where the condensation occurs (the ground, 30,000 feet), how it was made to occur (lifting, heating), and what the environment (winds, temperature, humidity, stability) is like in the areas immediately outside the cloud.

Finally, the existence of clouds alone doesn't always mean it will rain. The humidity must be high enough below the cloud to keep the raindrops from evaporating before they reach the ground. It is not unusual for clouds to begin raining while the surface remains dry, then slowly moisten the air below until finally the humidity rises enough that raindrops reach the ground.

There's a lot to digest in all these links. After you've done some more reading and research, feel free to ask more questions about humidity, clouds, and rain.