natu ha yuudati ga ooi kara, sentakumono wo soto ni dasippanasi ni suru to nuretyau.

は marks 夏 as the topic: As for summer, ... or In summer, ....

The sentence is making a general statement about summer, not identifying summer as the subject in contrast with something else. So 夏は sounds natural here.

If you used 夏が, it would usually sound like you were emphasizing summer itself, as if answering a question like Which season has a lot of evening showers?

夕立 means a sudden evening shower, often a short, heavy rain in the summer.

In 夕立が多い, the thing that is many/frequent is 夕立, so it takes が.
Japanese often uses X が多い for there are many X / X happens a lot.

So:

• 夕立が多い = there are many evening showers / evening showers are frequent

This is a very common pattern:

• 雨が多い = there is a lot of rain
• 人が多い = there are many people
• 仕事が多い = there is a lot of work

Both can be possible in some contexts, but X が多い is a very common and natural way to say that something is numerous or frequent.

Here, 夕立が多い sounds natural because it means evening showers happen a lot.

• 夕立が多い = evening showers are frequent
• 夕立がたくさんある = there are lots of evening showers

The second one is understandable, but 多い is the more standard phrasing here.

から means because.

The first part gives the reason:

• 夏は夕立が多いから = because there are many evening showers in summer

Then the second part gives the consequence:

• 洗濯物を外に出しっぱなしにするとぬれちゃう = if you leave the laundry outside, it’ll get wet

So the whole sentence is structured as:

• Because A, if B, then C

Here, から sounds natural and conversational.

洗濯物 means laundry, especially clothes or other things that are being washed or dried.

It often refers to physical laundry items, so in this sentence it means something like:

• the laundry
• your clothes you put out to dry

This is a very common question.

Here, 外に goes with 出す in 出しっぱなし.

• 出す = to put out / take out
• 外に出す = to put something outside

So に marks the destination or resulting location: to/outside.

Then 出しっぱなし means left out after putting it outside.

If you said 外で, that would emphasize the location where an action happens, such as:

• 外で洗濯物を干す = dry the laundry outside

But this sentence is specifically about putting it outside and leaving it there, so 外に is the natural choice.

出しっぱなし comes from:

• 出す = to put out
• っぱなし = leaving something as it is after doing it; not putting it back / not taking care of it afterward

So 出しっぱなし means:

• left out
• left sitting out
• left outside without bringing it in

It often has a nuance of carelessness or neglect.

Examples:

• 電気をつけっぱなし = leaving the lights on
• ドアを開けっぱなし = leaving the door open
• 洗濯物を出しっぱなし = leaving the laundry out

The pattern X にする often means to make something X or to leave something in state X.

So:

• 出しっぱなしにする = to leave it in the state of being left out

This is similar to:

• 静かにする = make it quiet / be quiet
• きれいにする = make it clean
• そのままにする = leave it as it is

So 出しっぱなしにする is literally something like to make it be in a left-out state, which naturally becomes to leave it out.

Here, と is a conditional meaning if / when.

It is often used when the result is:

• automatic
• natural
• predictable
• a general consequence

So:

• 洗濯物を外に出しっぱなしにすると、ぬれちゃう
• If you leave the laundry outside, it gets wet / it’ll get wet

This と fits well because the speaker is describing a normal consequence: leaving laundry outside in summer evening-shower season leads to it getting wet.

Compared with other conditionals:

• たら can sound more like a specific case
• なら is often based on a condition or assumption
• と is especially good for general truths or habitual results

Yes. ぬれちゃう is the casual spoken form of ぬれてしまう.

Breakdown:

• ぬれる = to get wet
• 〜てしまう = to end up doing; to do completely; often with regret or inconvenience
• ぬれてしまう → ぬれちゃう in casual speech

So ぬれちゃう means:

• it’ll end up getting wet
• it’ll get wet on you
• oops, it gets wet

There is often a slight feeling of annoyance, regret, or unfortunate result.

Using ぬれる would simply state the fact:

• ぬれる = it gets wet

Using ぬれちゃう adds the nuance that this is an unfortunate or undesirable outcome:

• ぬれちゃう = it ends up getting wet, unfortunately

Since getting the laundry wet is a bad result, 〜てしまう is very natural.

Because the sentence is talking about a general situation, not one specific event.

• 夏は夕立が多い = in summer, evening showers are frequent
• 出しっぱなしにするとぬれちゃう = if you leave it out, it gets wet / it’ll get wet

Japanese non-past forms often express:

• general truths
• habits
• repeated events
• future results

So this is like saying a general rule.

The subject is omitted because it is obvious from context. It is 洗濯物.

So the understood meaning is:

• 洗濯物を外に出しっぱなしにすると、洗濯物がぬれちゃう

Japanese very often leaves out subjects and objects when they are clear.

It can be understood as a general statement, like advice or a warning.

Something like:

• In summer, there are lots of evening showers, so if you leave the laundry outside, it’ll get wet.

So it is not necessarily one specific laundry load. It sounds more like a general habit/rule the speaker is pointing out.

Yes, depending on context.

Because と often expresses a natural consequence, English may translate it as either:

• if you leave the laundry outside, it gets wet
• when you leave the laundry outside, it gets wet

In this sentence, if is usually the most natural translation, but when can also work if you want to emphasize that it predictably happens.