ame no hi ha kami ga nakanaka kawakanai node, doraiyaa wo tukau zikan ga nagaku narimasu.

の links two nouns.

• 雨 = rain
• 日 = day
• 雨の日 = a rain day, more naturally a rainy day or a day when it rains

So this is a noun phrase. It is not the adjective 雨の by itself; rather, 雨 modifies 日 through の.

In Japanese, this pattern is very common:

• 夏の日 = a summer day
• 休みの日 = a day off
• 晴れの日 = a sunny day / clear day

In this sentence, 雨の日は means as for rainy days or on rainy days.

は marks the topic of the sentence.

So 雨の日は means something like:

• As for rainy days...
• On rainy days...

The speaker is setting the condition or situation being discussed. After that, the sentence explains what is true in that situation.

This is very natural in Japanese. English often uses adverbial phrases like on rainy days, while Japanese often uses a topic phrase with は.

Here, 髪が乾かない means the hair does not dry.

The particle が marks 髪 as the thing that undergoes the action/state of 乾かない. In other words, it marks what is not drying.

Compare:

• 髪が乾かない = the hair won’t dry / hair doesn’t dry
• 髪は乾かない = as for the hair, it doesn’t dry

Using が here is the most neutral and natural way to describe the specific thing affected by 乾かない.

So the sentence structure is roughly:

• As for rainy days, hair doesn’t dry easily, so...

Good question. なかなか has more than one use.

In this sentence, it is used with a negative verb:

• なかなか乾かない

This means:

• doesn’t dry easily
• doesn’t dry quickly
• just won’t dry

With a negative form, なかなか often means not easily or not readily.

Examples:

• なかなか終わらない = it doesn’t finish easily / it’s taking a long time to finish
• なかなか寝られない = I can’t fall asleep easily

It can also sometimes mean quite or rather, but that is a different usage and depends on context.

Because the sentence is saying that on rainy days, hair does not dry easily.

The dictionary form is:

• 乾く = to dry

Its negative plain form is:

• 乾かない = does not dry

Notice that 乾く is an intransitive verb. That means the hair dries by itself; you are not directly drying it as an object in this part of the sentence.

Compare:

• 髪が乾く = hair dries
• 髪を乾かす = dry one’s hair

So 髪がなかなか乾かない means hair does not dry easily.

Both can mean because, but ので often sounds a bit:

• softer
• more explanatory
• more neutral

So:

• 乾かないので = because it doesn’t dry
• 乾かないから = also because it doesn’t dry, but slightly more direct/conversational

In this sentence, ので fits very naturally because the speaker is explaining a result:

• Hair doesn’t dry easily on rainy days, so the time spent using a hair dryer becomes longer.

A rough feel:

• から = because (more direct)
• ので = since / because (more explanatory, gentler)

Both are possible, but they focus on slightly different things.

• ドライヤーを長く使います = I use the hair dryer for a long time
• ドライヤーを使う時間が長くなります = the time spent using the hair dryer becomes longer

The actual sentence talks about the length of time increasing. That is why it uses:

• ドライヤーを使う時間 = the time of using the hair dryer / the time spent using the hair dryer

This is a very common Japanese structure:

• verb + noun

Examples:

• 食べる時間 = time to eat / time spent eating
• 勉強する時間 = study time / time spent studying
• 寝る時間 = bedtime / time for sleeping

So 使う時間 is a noun phrase built from a verb plus a noun.

It is a relative-clause style modifier, which is extremely common in Japanese.

Break it down:

• ドライヤーを使う = use a hair dryer
• 時間 = time

Put them together:

• ドライヤーを使う時間 = the time when one uses a hair dryer / the time spent using a hair dryer

Japanese does not need words like that or when here. The verb phrase simply comes before the noun it modifies.

So this is not two separate clauses. It is one noun phrase.

Because the sentence is describing a change.

• 長い = long
• 長くなる = become long / get longer

So:

• 時間が長いです = the time is long
• 時間が長くなります = the time becomes longer

The speaker is saying that, because hair does not dry easily on rainy days, the time spent using the hair dryer increases.

That is why なる is important here.

Also note the adjective change:

• 長い → 長く before なる

This is how i-adjectives connect to verbs like なる:

• 高い → 高くなる = become expensive/high
• 早い → 早くなる = become early/faster
• 長い → 長くなる = become longer

This is very normal in Japanese.

Inside a sentence, verbs that modify nouns or come before connectors like ので often appear in plain form, even in polite speech.

So here:

• 乾かないので = because it doesn’t dry
• 使う時間 = the time spent using

The final verb is what determines the overall politeness level:

• 長くなります = polite

So the sentence is polite overall, even though some internal parts use plain forms. This is standard Japanese grammar, not a mismatch.

Yes, the subject is not fully spelled out, which is very common in Japanese.

The sentence literally talks about:

• rainy days
• hair
• the time spent using a hair dryer

But it does not explicitly say my, your, or I.

Depending on context, English might naturally translate it as:

• On rainy days, my hair doesn’t dry easily, so I end up spending longer using a hair dryer.
• On rainy days, hair doesn’t dry easily, so the time spent using a hair dryer gets longer.

Japanese often leaves out information that is clear from context.

Yes. 髪 can be understood either as:

• a specific person’s hair, if the context is personal
• hair in general, if the statement is more general

Japanese often leaves that open unless it needs to be specific.

So this sentence could be interpreted as:

• a general truth: On rainy days, hair doesn’t dry easily...
• a personal comment: On rainy days, my hair doesn’t dry easily...

Both are possible depending on context.

Because the sentence describes something that naturally becomes longer, not something someone intentionally makes longer.

• 時間が長くなる = the time becomes longer
• 時間を長くする = make the time longer

Here, the longer time is a result of the situation: rainy days make hair dry slowly, so the hair-dryer time increases. That is why なる is the natural choice.

A helpful breakdown is:

• 雨の日は = on rainy days / as for rainy days
• 髪がなかなか乾かないので、 = because hair does not dry easily
• ドライヤーを使う時間が長くなります。 = the time spent using a hair dryer becomes longer

So the whole structure is:

[Topic] + [Reason] + [Result]

More literally:

As for rainy days, because hair doesn’t dry easily, the time for using a hair dryer becomes longer.

That is a very common and natural Japanese sentence pattern.