natu ha amido wo simete okeba, soto no kaze dake irerareru.

夏は sets summer as the topic: as for summer or in summer.

It does not necessarily mean strong contrast by itself, but it can suggest speaking specifically about summer as opposed to other seasons. In this sentence, it frames the whole statement:

• 夏は = in summer / as for summer

So the rest of the sentence is understood as something that applies in that season.

網戸 is the screen door / screen panel / window screen—the mesh panel that lets air in while keeping insects out.

In Japanese homes, especially with sliding windows and doors, 網戸 often refers to the movable screened panel you slide shut. So 網戸を閉める means close the screen panel.

This can sound slightly odd in English if you imagine a fixed screen, but in Japanese it is completely natural.

Because 網戸 is the direct object of 閉めておけば.

• 網戸を閉める = to close the screen

So here:

• 網戸を閉めておけば = if you close the screen / if you leave the screen closed

The を marks the thing being acted on.

〜ておく often means:

1. do something in advance
2. do something and leave it that way

In this sentence, both ideas are relevant:

• 網戸を閉めておく = close the screen and leave it closed
• It also suggests doing this as a practical measure beforehand

So 閉めておけば means something like:

• if you keep the screen closed
• if you close the screen beforehand

Yes, there is a nuance difference.

• 閉めれば = if you close it
• 閉めておけば = if you close it and leave it that way / if you make a point of having it closed

〜ておく adds the idea of preparation or maintaining that state.

So 閉めておけば sounds more natural here, because the sentence is about setting things up so that only the breeze comes in.

The 〜ば form expresses if.

• 閉めておけば = if you close it and leave it closed

It often sounds a little more matter-of-fact or general than some other conditionals.

In this sentence, it gives a general result:

• If you keep the screen closed, then only the outside breeze can be let in.

So it is describing a typical consequence, not a one-time dramatic event.

Because the sentence is focusing on letting the wind in, not just the wind coming in by itself.

Compare:

• 風が入る = the wind comes in
• 風を入れる = let the wind in
• 風を入れられる = can let the wind in

Here the speaker is talking about what you are able to do by closing the screen:

• 外の風だけ入れられる = you can let in only the outside breeze

So 入れられる is the potential form of 入れる.

Yes, here it is best understood as the potential form of 入れる.

• 入れる = to put in / let in
• 入れられる = can put in / can let in

A passive reading would not make sense here. The sentence is about ability or possibility: by keeping the screen closed, you can let in only the breeze from outside.

Both can work, but the nuance is slightly different.

• 外の風 = the outside air / breeze from outside
• 外からの風 = wind coming from outside

外の風 is a very natural, compact way to say outside breeze/air. It sounds simple and everyday.

外からの風 would be a little more explicit, but the original version is completely normal.

だけ means only, and here it follows 風:

• 外の風だけ = only the outside breeze

So the idea is that, with the screen closed, what you allow in is just the breeze.

There is also an implied contrast, such as:

• breeze comes in
• bugs or other things do not

That implication fits naturally with 網戸.

Yes. Japanese often omits the subject when it is obvious or general.

Here, the sentence can be understood as something like:

• you can let in only the outside breeze
• one can let in only the outside breeze

The speaker is making a general statement, so there is no need to state you explicitly.

Grammatically yes: 閉める means to shut/close something.

But in real-life use, 網戸 is specifically the screen panel. So:

• 窓を閉める = close the window
• ドアを閉める = close the door
• 網戸を閉める = close the screen panel

In many Japanese homes, that means you keep the glass window open for airflow but slide the screen shut, so air comes in while insects stay out.

Both are possible, but they feel a little different.

• 風 = wind / breeze
• 空気 = air

Here 外の風 sounds more natural and pleasant in context, because the sentence is about enjoying airflow in summer. 風 suggests a refreshing breeze more than plain air does.

So 外の風だけ入れられる sounds very natural for this situation.

Yes, very strongly, even though it is not stated directly.

Because 網戸 is a screen, the listener naturally understands:

• the breeze can come in
• bugs are kept out

That is why the sentence says 外の風だけ. The only suggests that what gets through is the breeze, not unwanted things from outside.

Yes. That is a very good literal-style breakdown:

• 夏は = in summer
• 網戸を閉めておけば = if you keep the screen closed
• 外の風だけ = only the outside breeze
• 入れられる = can let in

That captures the structure well, even if a smoother English translation might be phrased a little differently.