xiān kàn tiānqìyùbào.

先 means first, beforehand, or to start with.

In 先看天气预报, it comes before the verb 看 because it tells you the action order: first, look at the weather forecast.

A very common pattern is:

先 + verb ... = first do ...

For example:

• 先吃饭。 = First eat.
• 先休息一下。 = First rest a bit.
• 先看天气预报。 = First check the weather forecast.

You will also often see the fuller pattern:

先...再... = first... then...

For example:

• 先看天气预报，再出门。 = First check the weather forecast, then go out.

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

So 先看天气预报。 could mean:

• I’ll first check the weather forecast.
• First check the weather forecast.
• We should first check the weather forecast.

The exact subject depends on the situation.

This is very normal in Mandarin. If needed, you could add a subject:

• 我先看天气预报。 = I’ll first check the weather forecast.
• 你先看天气预报。 = You first check the weather forecast.
• 我们先看天气预报。 = Let’s first check the weather forecast.

It can be either, depending on context and tone of voice.

With no subject, Chinese sentences like this are often flexible.

It can be:

• a statement: I’ll first check the weather forecast.
• a suggestion: Let’s first check the weather forecast.
• an instruction/command: First, check the weather forecast.

In writing, 。 just marks the end of the sentence. It does not by itself tell you whether the sentence is a command or statement.

In Chinese, 看 is a very broad verb. It can mean:

• look at
• watch
• read
• check

In 看天气预报, the most natural English translation is often check the weather forecast or watch the weather forecast, depending on context.

Examples:

• 看书 = read a book
• 看电视 = watch TV
• 看地图 = look at/check a map
• 看天气预报 = check/watch the weather forecast

So yes, 看 is broader than the English verb look.

天气预报 is a compound noun meaning weather forecast.

It is made of:

• 天气 = weather
• 预报 = forecast / forecast report

So literally it is something like weather forecast.

You can also see these parts in other words:

• 今天天气很好。 = The weather is good today.
• 预报说明天有雨。 = The forecast says it will rain tomorrow.

As a whole, 天气预报 is a fixed everyday word, and learners should memorize it as one vocabulary item.

It is written here as tiānqìyùbào.

The tones are:

• 天 tiān — first tone
• 气 qì — fourth tone
• 预 yù — fourth tone
• 报 bào — fourth tone

So the full pattern is:

tiān¹ qì⁴ yù⁴ bào⁴

A common difficulty is that the last three syllables are all fourth tone, so learners may blur them together. Try to keep each syllable clear:

tiān — qì — yù — bào

Also remember:

• 天气 is pronounced tiānqì, not tiānqi with a neutral tone.
• 预报 is yùbào, both fourth tone.

Mandarin does not have articles like a, an, and the.

So 天气预报 can mean:

• the weather forecast
• a weather forecast

Which one sounds best in English depends on context.

This is very common in Chinese. Nouns often appear without any article at all.

For example:

• 看书 = read a/the book(s), depending on context
• 买水果 = buy some/the fruit, depending on context
• 看天气预报 = check the weather forecast

English requires an article much more often than Chinese does.

Yes. 先看看天气预报 is very natural.

The extra 看 makes the tone softer and a bit more casual. This is a common pattern called verb reduplication.

Compare:

• 先看天气预报。 = First check the weather forecast.
• 先看看天气预报。 = First have a look at the weather forecast.

The reduplicated form often suggests:

• doing something briefly
• doing something in a lighter, less forceful way

So if you are making a suggestion, 先看看天气预报 can sound especially natural.

Yes. That is one of the most common ways to use 先.

You can extend it with 再 or 然后:

• 先看天气预报，再决定穿什么。 = First check the weather forecast, then decide what to wear.
• 先看天气预报，然后出门。 = First check the weather forecast, then go out.

A useful distinction:

• 先 = first
• 再 = then / after that
• 然后 = then / afterwards

So 先看天气预报。 can easily be the first half of a longer sequence.

Yes, depending on what you want to emphasize.

Common options include:

• 看天气预报 = watch/check the weather forecast
• 听天气预报 = listen to the weather forecast
• 查天气 = check the weather
• 查天气预报 = look up the weather forecast

The differences are small but useful:

• 看 suggests watching or checking it, often on TV or a screen.
• 听 suggests listening, for example on the radio.
• 查 suggests actively looking it up, often on a phone or online.

So 先看天气预报。 is perfectly natural, but other verbs are possible if the situation changes.