Learn Hardcore Turkish: Yarın sabah koşuya çıkmadan önce hava durumuna bakacağım. - Tomorrow morning, before going for a run, I will check the weather.

koşmak = to run (the basic verb, focusing on the action of running itself)
koşuya çıkmak = to go for a run, i.e. to go out with the intention of running

In daily speech, when people talk about their exercise routine, they usually say koşuya çıkmak.
Saying Yarın sabah koşacağım. is correct and understandable, but Yarın sabah koşuya çıkacağım. sounds more like “I’m going out for a run (as an activity/workout).”

How does -madan önce work in koşuya çıkmadan önce? Is -madan a negative form?

Yes. -madan is built from:

-ma- = negative marker
-dan (from -dAn) = an adverbial/ablative-type participle ending

Verb + -madan on its own means “without doing (the verb)”:

kitabı okumadan = without reading the book

When you add önce after it, Verb + -madan önce means “before doing (the verb)”:

koşuya çıkmadan önce = before going for a run
yemeği yemeden önce = before eating the meal

So in your sentence, çıkmadan önce = “before going out / before (I) go out.”

What’s the difference between -madan alone and -madan önce?

Verb + -madan = without doing X
- Hava durumuna bakmadan çıktım.
  = I left without checking the weather.
Verb + -madan önce = before doing X
- Hava durumuna bakmadan önce hazırlanıyorum.
  = I get ready before checking the weather.

In your sentence, koşuya çıkmadan önce clearly means “before going for a run”, not “without going for a run”, because of önce.

Why is it hava durumuna bakacağım, with hava durumu in the dative (-na)?

The verb bakmak normally takes the dative case: you “look to/at something”:

bir şeye bakmak = to look at something

So:

hava durumu = the weather (literally “the situation of the air”)
hava durumuna = to the weather (i.e. at the weather forecast/report)

That’s why we say hava durumuna bakmak (“to check the weather (forecast)”), not hava durumunu bakmak.
If you use hava durumunu, that would need a different verb, such as kontrol etmek:

hava durumunu kontrol edeceğim = I will check the weather (forecast).

What exactly is hava durumu? Why is it durumu, not just durum?

Hava durumu is a compound noun:

hava = air, but also “weather”
durum = situation, condition
durum‑u = “its situation” (3rd person possessive: “situation of it”)

So literally, hava durumu is “the weather’s situation”, i.e. the state of the weather → “the weather / the weather conditions / the weather forecast”.

The -u (durumu) is the standard way Turkish forms this kind of compound (“X’s situation/state”) and is not optional in this expression.
You don’t normally say hava durum; you say hava durumu.

Why is the ending in hava durumuna written as -na, not just -a?

Morphologically, it’s:

hava durumu (weather)
- -a (dative case)
plus a buffer consonant -n- between two vowels

So:

durum‑u + a → durumua, which is hard to pronounce
Turkish inserts n → durumu‑na

This n is a standard buffer consonant used in Turkish when a vowel-ending word takes a vowel-starting suffix, especially after 3rd person possessive endings (-ı, -i, -u, -ü → -nı, -ni, -nu, -nü, etc.).
The same thing happens in ev‑i‑ne → evine (“to his/her house”), but if you add another vowel-starting suffix after evi, you get evi‑ne, evi‑ni, etc. with a buffer n.

How is bakacağım formed, and how do you pronounce it?

Formation:

bak- = look
-acak = future tense suffix (after back vowels: a, ı, o, u)
-ım = 1st person singular ending (“I”)

Together: bak + a + cak + ım → bakacağım.

Pronunciation:

Written ğ is usually not pronounced as a full consonant; it lengthens the preceding vowel.
bakacağım is roughly pronounced [bakaˈʤaːm] (“baka-jaam”).

So it sounds more like “baka-jaam” than “bakagajım”.
It means “I will look / I will check.”

Why is there no separate word for “will” in bakacağım?

Turkish does not use a separate auxiliary verb like “will”.
Instead, tense and person are expressed by suffixes on the main verb:

bakacağım = bak- (look) + -acak (future) + -ım (I)
→ I will look
bakacaksın = you will look
bakacak = he/she/it will look

So “will” is embedded inside the verb as the future tense suffix (-acak / -ecek), rather than being a separate word.

Could I say Yarın sabah hava durumuna bakacağım, koşuya çıkmadan önce with the clauses reversed?

Yes. Turkish word order is relatively flexible, and both are grammatical:

Yarın sabah koşuya çıkmadan önce hava durumuna bakacağım.
Yarın sabah hava durumuna bakacağım, koşuya çıkmadan önce.

The default / more neutral version is the first one, where the time clause koşuya çıkmadan önce directly precedes the main action hava durumuna bakacağım.
Putting koşuya çıkmadan önce at the end can add a slight emphasis on the “before going for a run” part, but the meaning is basically the same.

Why is it yarın sabah, and not something like sabah yarın?

For combinations like “tomorrow morning, yesterday evening”, Turkish typically uses the pattern:

yarın sabah = tomorrow morning
yarın akşam = tomorrow evening
dün akşam = yesterday evening
bu sabah = this morning

The time word (yarın, dün, bu) usually comes before sabah / akşam / gece.
So sabah yarın is not natural; yarın sabah is the normal phrase.

Could I say Yarın sabah koşmadan önce hava durumuna bakacağım instead of koşuya çıkmadan önce?

Yes, Yarın sabah koşmadan önce hava durumuna bakacağım is grammatically correct and understandable:

koşmadan önce = before running

However, koşuya çıkmak is more idiomatic when you mean “go out for a run (as an activity)”.
So:

koşmadan önce → focuses directly on the act of running
koşuya çıkmadan önce → focuses on “going out for a run” (starting the running session)

In everyday speech about workouts, koşuya çıkmak sounds more natural.

Why do both koşuya and durumuna have -a/-ya/-na endings? Are they the same suffix?

Yes, both are forms of the dative case (-A, realized as -a or -e depending on vowel harmony):

koşu + a → koşuya (dative: to/towards the run)
durum + u + a → durumua → durumuna (dative with buffer n)

They look slightly different because of:

Vowel harmony
- After a back vowel: -a (koşu → koşuya)
- After a front vowel: -e (for example: şehir → şehre)
Buffer consonants (like y and n) inserted to avoid vowel clashes:
- koşu + a → koşua → koşuya
- durumu + a → durumua → durumuna

So -a / -e / -ya / -ye / -na / -ne here are all surface forms of the same underlying dative suffix -A.