Weather in English, for example: when does rain snow use the ing form. When to use the noun form. When to add s. When to use prototypes

Use ing to express the continuous tense and noun form respectively. For example, it's raining now! and raining is heavy today! Add s to express the present tense. For example, it rains today! (Rain is an uncountable noun, so you cannot add s. Usually, s is added to express the present tense.

Use the original form, such as there is a little rain!