Which of the following is NOT a form of precipitation?

Humidity is not a form of precipitation; rather, it refers to the amount of water vapor present in the air. Precipitation specifically involves any form of water, liquid or solid, that falls from the atmosphere to the Earth's surface. This includes forms such as rain, snow, and hail, which are direct manifestations of moisture condensing and falling due to gravity.

In contrast, humidity is a measure of how much moisture is in the air and does not itself fall from the atmosphere in any physical form. It plays a role in forming precipitation but is distinct from the actual events of rain, snow, or hail, which are characterized by their physical state and occurrences. Thus, understanding this distinction clarifies why humidity does not qualify as a type of precipitation.