Learn Hardcore Russian: Сезон дождей становится прохладным.

It literally translates to "season of rains." The noun дождей is the genitive plural of дождь and is used here to specify what type of season it is—that is, a season characterized by rain. In Russian, modifying nouns that describe a characteristic or a possession take the genitive case.

Why is the adjective прохладным in the instrumental case rather than the nominative?

When a Russian sentence uses a linking verb like становиться (to become), the predicate adjective describing the new state is placed in the instrumental case. Thus, прохладным is in the instrumental to indicate the state that Сезон дождей is becoming.

What is the function of the verb становляется in this sentence, and what tense and aspect does it express?

Становляется is the third-person singular form of становиться, meaning "to become." It is in the present tense and is an imperfective verb, which conveys an ongoing or gradual change of state, linking the subject to its new attribute.

How do the cases in Сезон дождей and прохладным work together grammatically?

The subject Сезон is in the nominative case, while дождей is in the genitive case, modifying the noun to specify the type of season (a season of rains). The adjective прохладным is in the instrumental case to meet the grammatical requirement of the linking verb становиться, which calls for a predicate complement that describes the changed state.

Can the idea of a "rainy season" be expressed differently in Russian, and why might one choose the phrase Сезон дождей over another option?

Yes, you could also say дождливый сезон, where дождливый is an adjective meaning "rainy." However, Сезон дождей is often preferred because it emphasizes the characteristic of being defined by numerous rains. This noun phrase construction can provide a more vivid or specific description, highlighting the natural phenomenon that marks the season.