Trời vẫn có gió lạnh vào buổi sáng, nhưng đến trưa thì nắng đẹp hơn nhiều.

Here trời does not literally mean just the sky. In everyday Vietnamese, trời is very often used in weather expressions and works more like the weather / it in English.

So:

• Trời vẫn có gió lạnh... = It is still cold and windy... / The weather is still windy and cold...

Vietnamese often uses trời where English uses the dummy subject it, as in:

• Trời nóng. = It’s hot.
• Trời mưa. = It’s raining.

So in this sentence, trời is a natural weather subject.

Vẫn means still.

It shows that a situation continues from before into the time being talked about.

So:

• Trời vẫn có gió lạnh vào buổi sáng
  = In the morning, there is still a cold wind
  = The weather is still cold and windy in the morning

It suggests that the cold wind has not gone away yet.

Có often means to have, but it also commonly means there is / there are depending on context.

So:

• trời có gió lạnh literally looks like the weather has cold wind
• but natural English is there is a cold wind or it is cold and windy

This is a very common Vietnamese pattern:

• Có mưa. = There is rain / It’s raining.
• Có gió. = There is wind / It’s windy.

So here có is introducing the weather condition.

Literally, gió lạnh means cold wind.

• gió = wind
• lạnh = cold

But in natural translation, English speakers may express the whole idea more smoothly as:

• there is a cold wind
• it’s chilly and windy
• the morning is still cold and windy

So the phrase specifically mentions wind, but the overall feeling is a chilly morning.

Yes, buổi sáng alone is often possible.
Vào buổi sáng is slightly more explicit and means in the morning.

• vào = at / in / during, depending on context
• buổi sáng = morning

So:

• vào buổi sáng = in the morning
• buổi sáng can also mean in the morning, especially when the time phrase is obvious from context

Both are natural, but vào makes the time relationship clearer.

Nhưng means but.

It connects the two contrasting parts of the sentence:

• Trời vẫn có gió lạnh vào buổi sáng
  = the morning is still cold/windy
• nhưng đến trưa thì nắng đẹp hơn nhiều
  = but by noon the sunshine/weather becomes much nicer

So nhưng marks a clear contrast between morning and noon.

Đến trưa literally means arriving at noon or when it gets to noon.

In natural English, depending on context, it can be:

• by noon
• at noon
• when noon comes
• toward noon

In this sentence, đến trưa suggests a change by the time noon arrives:

• morning: still cold and windy
• noon: the sunshine is much nicer

So by noon is often a very good translation.

Thì often does not have a single direct English translation. It is a very common topic/comment or contrast marker.

In this sentence, thì helps separate the time phrase from what happens at that time:

• đến trưa thì nắng đẹp hơn nhiều

It gives a sense like:

• as for noon,
• then by noon,
• at noon, however,

It makes the sentence flow naturally and highlights the contrast with the morning part.

Vietnamese often uses thì after a topic or time phrase:

• Buổi sáng thì mát. = As for the morning, it’s cool.
• Chiều thì đông hơn. = In the afternoon, it’s more crowded.

So here it is grammatical and very natural, even if English often leaves it untranslated.

Literally, đẹp means beautiful / pretty, but in weather expressions nắng đẹp is a very natural Vietnamese phrase.

It means things like:

• nice sunshine
• good sunlight
• pleasant sunny weather
• the sun is out nicely

So nắng đẹp hơn nhiều does not sound poetic or strange in Vietnamese. It simply means the sunshine/weather is much nicer than before.

This is one of those places where a literal word-for-word translation sounds less natural than the real meaning.

Hơn means more or marks a comparison: -er / more ... than before.

• đẹp hơn = more beautiful / nicer

Nhiều after a comparative strengthens it and means much / a lot.

So:

• đẹp hơn = nicer
• đẹp hơn nhiều = much nicer

In this sentence:

• nắng đẹp hơn nhiều = the sunshine is much nicer

It emphasizes a strong improvement by noon.

Yes. The comparison is implied by context.

The sentence first describes the morning as still having gió lạnh, then says that by noon nắng đẹp hơn nhiều. So the comparison is basically:

• nicer than in the morning
• nicer than before

Vietnamese often leaves the comparison target unstated when it is obvious from the previous clause.

Yes. A very literal breakdown is useful for learning, but natural English might sound like:

• It’s still cold and windy in the morning, but by noon the sunshine is much nicer.
• The mornings are still chilly and windy, but by noon it gets much sunnier and nicer.
• There’s still a cold wind in the morning, but by noon the weather is much better.

The exact English wording can vary, but the Vietnamese sentence is describing a change in weather from morning to noon.

The sentence has two main clauses joined by nhưng:

1. Trời vẫn có gió lạnh vào buổi sáng

   • Trời = weather / it
   • vẫn = still
   • có gió lạnh = has cold wind / there is a cold wind
   • vào buổi sáng = in the morning

2. nhưng đến trưa thì nắng đẹp hơn nhiều

   • nhưng = but
   • đến trưa = by noon / when noon comes
   • thì = topic/contrast marker
   • nắng đẹp hơn nhiều = the sunshine is much nicer

So the overall pattern is:

morning condition + but + noon condition

This is a very common and useful Vietnamese sentence pattern for contrasts across times of day.