tiānqì yíhuìr xiàyǔ, yíhuìr guāfēng.

In this sentence, 一会儿……一会儿…… means one moment... and the next... or now... now.... It shows that something keeps changing back and forth over a short period of time.

So the sentence means the weather is unstable: one minute it rains, the next minute it gets windy.

The repetition is what creates the pattern of alternation.

• 一会儿下雨 = for a moment, it rains / one moment it rains
• 一会儿刮风 = then for a moment, it gets windy / the next moment it gets windy

If you used only one 一会儿, it would usually mean in a little while, for a moment, or for a short time, not this alternating back-and-forth meaning.

天气 is the topic of the sentence.

Chinese often uses a topic-comment structure:

• 天气 = as for the weather
• 一会儿下雨，一会儿刮风 = it rains one moment, gets windy the next

So the whole sentence is like:

As for the weather, one moment it rains, the next moment it gets windy.

This is very natural in Chinese.

Because Chinese often leaves out the subject when it is obvious from context.

In English, we say:

• It is raining
• It is windy

But in Mandarin, you usually do not need a dummy subject like it. Once 天气 sets the topic, Chinese can go straight to the weather actions:

• 下雨 = rain / to rain
• 刮风 = wind blows / to be windy

So leaving out it is completely normal.

Because 下雨 and 刮风 are not adjective phrases that need is. They are verbal expressions.

• 下雨 = to rain
• 刮风 = the wind blows / to be windy

So Chinese does not say something like 天气是下雨. That would sound wrong.

A helpful way to think about it:

• English: It is raining
• Chinese: (It) rains

Yes, they function as verbs or verbal phrases.

More literally:

• 下雨 = rain falls
• 刮风 = wind blows

Even though they contain nouns (雨, 风), the whole expressions act like verbs and can be used directly as predicates in a sentence.

That is why you can say:

• 今天下雨。
• 外边刮风。

without needing another main verb.

Not literally. Literally, 刮风 means the wind blows. But in natural English, it is often translated as it’s windy.

So:

• literal idea: the wind is blowing
• natural English meaning: it’s windy

In weather sentences, English often uses adjectives, while Chinese often uses verb-like expressions.

This is because of the tone change rule for 一.

Normally, 一 is first tone: yī.
But before a fourth-tone syllable, it changes to second tone: yí.

Since 会 is fourth tone (huì), 一会儿 is pronounced:

yíhuìr

This is a very common pronunciation rule in Mandarin.

No. 一会儿 can have a few related meanings depending on context.

Common uses include:

• a little while / a moment
  
  • 等一会儿。 = Wait a moment.
• in a little while
  
  • 我一会儿去。 = I’ll go in a little while.
• one moment..., the next... when repeated
  
  • 一会儿下雨，一会儿刮风。

So the repeated pattern gives it a special meaning of changing from one state to another.

The 儿 is an erhua ending, a common pronunciation feature in Standard Mandarin and especially northern speech.

So 一会儿 is often pronounced with that -r sound:

• yíhuìr

In some places, you may also hear 一会 without the 儿 sound. The meaning is basically the same.

For learners, it is useful to recognize both, but 一会儿 is very common in standard spoken Mandarin.

You could, but the meaning would be different.

• 一会儿下雨，一会儿刮风 = one moment it rains, the next it gets windy
  → emphasizes alternation and change over time

• 又下雨又刮风 = it’s both raining and windy
  → often suggests the two things are happening together

So the original sentence focuses on the weather being changeable, not just on both conditions existing.

The comma separates the two parallel parts of the 一会儿……一会儿…… pattern:

• 一会儿下雨
• 一会儿刮风

In Chinese writing, commas are often used to divide clauses like this very naturally. It helps show the rhythm and balance of the sentence.