Learn Hardcore Chinese: tiānqì rè de shíhou, tā xǐhuan hē lěng shuǐ, wǒ xǐhuan hē rè chá. - When it’s hot, she likes to drink cold water; I like to drink hot tea.

的 links an attributive clause to a noun. Here, 天气热 (the weather is hot) modifies the noun 时候 (time/moment), so 天气热的时候 means “the time when the weather is hot.” Pattern: clause + 的 + noun, e.g. 我不在家的时候, 你来的时候.

Can I omit 的 and say 天气热时候?

No—without 的 it’s ungrammatical/nonnative. Acceptable alternatives:

天气热的时候 (standard)
天气热时 (more formal/literary)
天热的时候 (colloquial; see below about 天 vs 天气)

Do I need 很 in 天气热的时候?

Not required. In predicate adjective sentences, a degree adverb like 很 often appears, but in the …的时候 structure, 很 is optional:

Neutral: 天气热的时候
Emphatic: 天气很热的时候, 天气特别热的时候

Could I just say 天气热，她喜欢喝冷水 and drop 的时候?

Yes. 天气热，… works as a general time/cause setting. You can add 就 to highlight the natural response: 天气热，她就喜欢喝冷水.

Why isn’t there a 是 in 天气热的时候?

Chinese adjectives can be predicates without 是. You don’t say 天气是热的时候. Use 是 for identity/classification, not to link adjectives to subjects.

Where can I put the time clause?

Common placements:

Fronted (most natural): 天气热的时候，她喜欢喝冷水。
Before the verb with 在: 她在天气热的时候喜欢喝冷水。
Before the object: 她喜欢在天气热的时候喝冷水。 End-position is possible but marked: 她喜欢喝冷水，在天气热的时候。

What’s the difference among 天气热的时候, 天气热时, and 当天气热的时候?

…的时候: neutral, everyday.
…时: concise, formal/literary.
当…的时候: adds emphasis on “when.” Some consider 当…的时候 slightly redundant, but it’s very common.

Why 时候 and not 时间?

时候 = a moment/occasion (“when …”). It attaches naturally to clauses with 的: 我到家的时候.
时间 = time as an amount/availability. You don’t say 天气热的时间 to mean “when it’s hot.”

What’s the difference between 冷水, 冰水, and 凉水?

冷水: cold water (feels cold).
冰水: iced water / water with ice; very cold.
凉水: cool water; in some regions (e.g., North China) often means room‑temperature/unheated drinking water.

Why no 的 in 冷水 and 热茶?

Monosyllabic adjectives (like 冷, 热) often modify nouns directly: 冷水, 热茶. Use 的 when:

The modifier is polysyllabic: 刚烧开的水, 非常热的茶.
You want to emphasize/state a temporary property: 热的茶 (the tea that is hot).

Can I say 热的茶 or 冷的水?

Yes. 热茶/冷水 are a bit tighter; 热的茶/冷的水 slightly highlight the state. When the noun is understood, keep 的 and drop the noun: 她喜欢喝冷的，我喜欢喝热的.

Is 喜欢 + verb phrase (e.g., 喜欢喝冷水) okay? Why not just 喜欢冷水?

Both are fine but differ:

喜欢喝冷水: you like the action of drinking it (habit/preference).
喜欢冷水: you like cold water as a thing/concept; may or may not imply drinking.

Could I use 爱 instead of 喜欢?

Yes, but nuance changes:

喜欢: like, prefer (neutral).
爱: love; sounds stronger or more colloquial in habits: 她爱喝冷水 = “She loves to drink cold water.”

Should I add 就 after the time clause?

Optional. 就 shows a natural or immediate result: 天气热的时候，她就喜欢喝冷水. Without 就, it’s a plain statement of habit.

Do I need a conjunction between the two clauses to show contrast?

Not required, but you can add one to highlight contrast:

…，而我喜欢喝热茶。
…，我却喜欢喝热茶。
…，但是我喜欢喝热茶。
…，我则喜欢喝热茶。

Is 在 necessary in 在…的时候?

No. …的时候 is enough. 在…的时候 is also common and a bit heavier/explicit as a time prepositional phrase.

Can I use 天 instead of 天气?

Yes:

天热的时候 (very colloquial)
天气热的时候 (neutral/standard) Also common as a plain predicate: 天热了 = “It has become hot.”

Pronunciation check: tones for key words?

时候: shíhou (2nd tone + neutral)
喜欢: xǐhuan (3rd + neutral)
的: de (neutral)
喝: hē (1st)
冷: lěng (3rd)
热: rè (4th)
茶: chá (2nd)
天气: tiānqì (1st + 4th)

Do I need measure words for water/tea here?

Not when speaking generally. For specific amounts, use a measure word:

一杯热茶 (a cup of hot tea)
一瓶冰水 (a bottle of iced water)
喝一口水 (take a sip of water)

Should I use 喝 or 吃 for beverages?

Use 喝 for liquids you drink: 喝水, 喝茶, 喝汤. 吃 is for foods you chew; it’s not used for water/tea in standard Mandarin.