Learn Hardcore Indonesian: Saya tidak mau keluar ketika hujan deras. - I do not want to go out when it is raining heavily.

tidak is used before:
- verbs: tidak mau (do not want)
- adjectives: tidak besar (not big)
bukan is used before:
- nouns: bukan dokter (not a doctor)
- pronouns: bukan saya (not me)

In tidak mau, mau is a verb (want), so tidak is correct.
bukan mau would be ungrammatical here.

What is the nuance of mau in this sentence? Is it only “want to”?

In this sentence, mau mostly means want (to):

tidak mau keluar = do not want to go out

Nuances of mau:

Basic meaning: want (to)
- Saya mau makan. = I want to eat.
Colloquial future meaning (going to)
In casual speech, mau can sometimes mean about to / going to:
- Saya mau pergi. = I’m about to go / I’m going to go.

In Saya tidak mau keluar ketika hujan deras, it is clearly about desire/willingness:
I don’t want to go out when it’s raining heavily (I refuse / I prefer not to).

Could I use ingin instead of mau? Is there a difference?

Yes, you can say:

Saya tidak ingin keluar ketika hujan deras.

Differences:

mau
- Very common in everyday speech.
- Neutral or slightly casual.
- Can also give a sense of about to in some contexts.
ingin
- A bit more formal or literary.
- Feels slightly stronger or more deliberate, like desire or wish.
- Less used in very casual conversations.

Meaning-wise, both are acceptable here; the sentence stays understandable and natural with either one. Mau is more common in daily conversation.

Why isn’t there a word for “it is” before “raining” like in English?

Indonesian doesn’t need an equivalent of it is in weather expressions.

hujan can mean both rain (noun) and to rain (verb).
Saying hujan by itself can mean it’s raining.

So:

hujan deras = heavy rain / raining heavily
ketika hujan deras = when (it is) raining heavily

The subject it and the verb is in English are simply not expressed in Indonesian; the phrase hujan deras is enough.

What is the role of keluar here? Could I use pergi instead?

keluar = to go out / to exit (from an inside space to outside)
pergi = to go (away), not necessarily “out” of a place

In this context:

tidak mau keluar = don’t want to go outside (implies from indoors to outdoors)
tidak mau pergi = don’t want to go (anywhere)

You could say:

Saya tidak mau pergi ketika hujan deras.

That would mean I don’t want to go (anywhere) when it’s raining heavily, which is fine, but a bit less specific about “going outside”.
keluar matches the idea of going out into the rain more directly.

Why is ketika used? Can I also say saat, waktu, or kalau? Do they mean the same?

Here are the common options and their feel:

ketika
- Neutral, a bit more formal / written.
- Literally when / at the time that.
- Good in narratives or careful speech.
saat
- Very common, slightly formal-neutral.
- Similar to at the moment when.
- Saya tidak mau keluar saat hujan deras.
waktu
- Originally means time, but often used as when in speech.
- Slightly more casual than ketika.
- Saya tidak mau keluar waktu hujan deras.
kalau
- Literally if, but often used as when in everyday conversation.
- Can sound very casual here:
- Saya tidak mau keluar kalau hujan deras.

All four can work in this sentence; ketika is a safe, neutral choice.
In casual speech, you’ll probably hear kalau or waktu a lot.

What exactly does deras mean, and why does it come after hujan?

deras means heavy, fast-flowing, intense (for rain, water, sometimes wind).
hujan deras = heavy rain / pouring rain / raining heavily.

Word order:
In Indonesian, adjectives usually come after the noun:

hujan deras = rain heavy
orang tinggi = tall person
rumah besar = big house

So deras follows hujan because it is describing the rain.

Could I omit saya and just say Tidak mau keluar ketika hujan deras?

Yes, you can.

Indonesian often drops subject pronouns when the context is clear. So:

Saya tidak mau keluar ketika hujan deras.
Tidak mau keluar ketika hujan deras.

Both can be understood as I don’t want to go out when it’s raining heavily, if context makes it obvious you are talking about yourself.

Including saya makes the subject explicit; omitting it is quite natural in conversation when everyone already knows who is being discussed.

Is the word order fixed, or can I move the ketika-clause to the front?

You can move the time clause to the front without changing the meaning:

Saya tidak mau keluar ketika hujan deras.
Ketika hujan deras, saya tidak mau keluar.

Both are correct and natural.

Putting ketika hujan deras at the beginning:

Emphasizes the time condition (when it’s raining heavily).
Feels slightly more formal or story-like, but still common.

Just remember to keep the words inside each part in the same order; you only move the whole time clause.

How do I show past or future time? This sentence looks “timeless”.

Indonesian verbs do not change form for tense. Time is usually shown by context or time words:

Present / general habit (like your original sentence):
- Saya tidak mau keluar ketika hujan deras.
- I don’t want to go out (whenever) it’s raining heavily / I don’t like doing that.
Past:
- Tadi saya tidak mau keluar ketika hujan deras.
  - tadi = earlier / a while ago
- Kemarin saya tidak mau keluar ketika hujan deras.
  - kemarin = yesterday
Future:
- Besok saya tidak mau keluar kalau hujan deras.
  - besok = tomorrow
- Or add akan before the verb:
  - Saya tidak akan mau keluar kalau hujan deras. (I will not want to go out if it’s raining heavily.)

The basic structure tidak mau keluar ketika hujan deras stays the same; you add time words like tadi, tadi pagi, kemarin, besok to show tense.