Toàn thành phố sẽ có mưa.

Toàn thành phố means the whole city or the entire city.

In this sentence, it gives the idea of location/coverage: the rain is expected throughout the city, not just in one area.

• toàn = whole, entire
• thành phố = city

So toàn thành phố = the whole city / across the whole city

In Vietnamese, words like toàn often come before the noun they modify.

So:

• toàn thành phố = the whole city
• not thành phố toàn

This is similar to English the entire city, where entire also comes before city.

They are very close in meaning. Both can mean the whole city.

However, there is a slight difference in feel:

• toàn thành phố often sounds a bit more formal or suitable for reports/forecasts
• cả thành phố is very common in everyday speech

So in a weather forecast, Toàn thành phố sẽ có mưa sounds very natural.

Sẽ is a future marker. It usually means will.

So:

• có mưa = there is rain / rain occurs
• sẽ có mưa = there will be rain / it will rain

Vietnamese does not always need a future marker, but sẽ is used when the speaker wants to clearly show that the event is in the future.

Both patterns exist, but they are used a little differently.

• có mưa literally means have rain or there is rain
• In weather language, it means there will be rain / rain is expected

This is a very common forecast-style structure in Vietnamese.

Compare:

• Hôm nay mưa. = It’s raining today / Today is rainy.
• Ngày mai sẽ có mưa. = There will be rain tomorrow / It will rain tomorrow.

So có mưa can sound a bit more like a report or prediction.

Here, mưa behaves more like a noun inside the expression có mưa.

• mưa by itself can act like to rain
• but in có mưa, it is closer to rain as a thing/event

So:

• Trời mưa. = It is raining.
• Sẽ có mưa. = There will be rain.

This flexibility is very common in Vietnamese.

A rough breakdown is:

• Toàn thành phố = the whole city
• sẽ = will
• có = have / there be
• mưa = rain

So literally, it is something like:

The whole city will have rain.

That sounds a bit unusual in natural English, but it is a normal Vietnamese way to express It will rain across the whole city.

Yes, but it may not work exactly like an English subject.

In Toàn thành phố sẽ có mưa, the phrase toàn thành phố is the topic/location being talked about: the whole city.

Vietnamese often allows location phrases to appear at the front very naturally, especially in weather statements.

So the sentence is not really about the city doing something. It means that within the whole city, rain will occur.

Yes. Khắp thành phố sẽ có mưa is also natural and means There will be rain throughout the city.

A few similar expressions are:

• Toàn thành phố sẽ có mưa.
• Khắp thành phố sẽ có mưa.
• Cả thành phố sẽ có mưa.
• Sẽ có mưa trên toàn thành phố.

They are all similar, but the nuance changes slightly:

• toàn thành phố = the whole city
• khắp thành phố = throughout the city / all over the city
• trên toàn thành phố = across the entire city, often more formal

Yes, sometimes you can, depending on context.

• Toàn thành phố có mưa. can mean The whole city has rain or, in a forecast context, The whole city is expected to have rain
• Toàn thành phố sẽ có mưa. clearly means The whole city will have rain

So sẽ makes the future meaning more explicit. In forecasts and predictions, keeping sẽ is often helpful.

Yes, it is natural, especially in a weather-report style.

It sounds a bit like something you would hear in:

• a weather forecast
• a news report
• a formal announcement

In casual speech, people might also say things like:

• Mai cả thành phố có mưa.
• Ngày mai khắp thành phố sẽ mưa.
• Ngày mai trời sẽ mưa khắp thành phố.

But Toàn thành phố sẽ có mưa is absolutely normal and clear.

A careful pronunciation would be roughly:

Toàn thành phố sẽ có mưa
≈ twahn thahn-phoh seh kaw moo-uh

A few notes:

• toàn has a falling tone
• thành has a low tone
• phố has a rising-broken tone
• sẽ has a creaky/rising tone
• có has a rising tone
• mưa has a level tone

The exact pronunciation depends on dialect, but the biggest thing is to pay attention to the tones, especially in phố, sẽ, and có.