What is the correct statement for describing precipitation in the form of water falling from the sky?

The statement that describes precipitation in the form of water falling from the sky is "It's raining." This accurately conveys that water droplets are falling from the atmosphere, which is the essence of rain. Precipitation specifically refers to any form of water—liquid or solid—that falls from clouds in the atmosphere and reaches the ground, and rain is one of the most common types of precipitation.

The other options do not directly describe precipitation. Windiness can be a characteristic of weather conditions but does not indicate whether water is falling. Cloudiness suggests the presence of clouds, which are often associated with rain, but doesn't confirm that it is actually raining. Hot temperatures can occur during various weather conditions but are unrelated to precipitation occurring in the form of rain. Thus, "It's raining" is the most precise and relevant description of the phenomenon of water falling from the sky.