Learn Hardcore Turkish: Bugün hava o kadar güzel ki bütün gün dışarıda kalmak istiyorum. - Today the weather is so nice that I want to stay outside all day.

O kadar yorgunum ki konuşacak hâlim yok.
I’m so tired that I have no energy to talk.
O kadar hızlı konuştu ki hiçbir şey anlamadım.
He spoke so fast that I didn’t understand anything.

Çok just means very and doesn’t automatically introduce a result:

Bugün hava çok güzel.
The weather is very nice today. (statement, no “that…” result)
So in your sentence, o kadar … ki emphasizes that the weather is so nice that it causes the desire to stay outside all day.

Why do we say hava for “the weather” instead of something like “it” (as in “it is nice today”)?

In English, we say “It is nice today” with a dummy subject it that doesn’t refer to anything specific.

In Turkish, there is no dummy “it” like this. Instead, Turkish uses a real noun:

hava = air / weather

So:

Bugün hava güzel.
Literally: Today the weather beautiful.
Meaning: The weather is nice today / It’s nice today.

You can sometimes also say:

Bugün çok güzel hava var.
Literally: Today there is very nice weather.

But you can’t say something like “Bugün o kadar güzel ki…” without mentioning what is so nice. You need hava there:

Bugün hava o kadar güzel ki… ✅

What is the role of ki here? Is it the same ki that I see in other places in Turkish?

In this sentence, ki is a conjunction that works like English “that” in the structure “so … that …”.

o kadar güzel ki bütün gün dışarıda kalmak istiyorum
→ so nice that I want to stay outside all day

This ki:

connects a reason/intensity part (o kadar güzel) to a result part (bütün gün dışarıda kalmak istiyorum)
is written separately as a word.

There are two common ki’s in Turkish:

Conjunction ki (like here)
- O kadar yorgunum ki uyumadan duramıyorum.
  I’m so tired that I can’t stay awake.
Suffix -ki (attached, meaning “that, which belongs to”)
- dünkü = yesterday’s, the one from yesterday
- evdeki = the one in the house
- şu andaki = at this moment

So in your sentence it’s the conjunction ki used with o kadar … ki.

Why is it dışarıda and not dışarı or dışarıya?

This is about location vs. movement.

dışarı: “outside” (more abstract / direction, often without case)
dışarıya: “to outside” (-a / -e = direction, to)
dışarıda: “outside” (-da / -de = location, in/at/on)

In your sentence:

bütün gün dışarıda kalmak istiyorum
Literally: I want to stay outside all day.

Here, kalmak = to stay / to remain → this describes being in a place, not going to a place, so you need the locative case:

dışarıda kalmak = to stay outside ✅
dışarıya kalmak ❌ (mixes “to outside” with “stay” – doesn’t work)
dışarı kalmak: possible in some specific expressions, but sounds incomplete/odd here.

If there were movement, you’d use dışarıya:

Dışarıya çıkmak istiyorum.
I want to go out / go outside.

What form is kalmak, and why does it end in -mak?

Kalmak is the dictionary form / infinitive of the verb kal- (“to stay, remain”).

In Turkish, infinitives are formed with:

-mak / -mek

Choice of -mak or -mek depends on vowel harmony; kal- has a, so it takes -mak:

kalmak: to stay
gelmek: to come
yapmak: to do
görmek: to see

In the sentence, kalmak is used as the object of the verb istiyorum:

bütün gün dışarıda kalmak istiyorum
Literally: I want staying outside all day.
More natural English: I want to stay outside all day.

So structurally, it’s:

[kalmak] = the thing you want (a verbal noun)
istiyorum = I want

Why is it istiyorum and not something like isterim or just istiyorum kalmak?

İstemek = to want. To say “I want”, you conjugate it:

istiyorum = I want (present continuous form)
isterim = I want / I would want (aorist form, often more general or formal)

In everyday spoken Turkish, istiyorum is the most common for real, current desires:

Su istiyorum. → I want (some) water.
Gitmek istiyorum. → I want to go.

So bütün gün dışarıda kalmak istiyorum = “I want to stay outside all day.”

As for word order, you must put the thing you want (the infinitive) before istiyorum:

kalmak istiyorum ✅
istiyorum kalmak ❌ (ungrammatical in standard Turkish)

What does bütün gün mean exactly? Is it different from tüm gün?

Both bütün gün and tüm gün mean “all day” / “the whole day”.

bütün = whole, entire
tüm = all, entire

In this context:

bütün gün = all day, the whole day
tüm gün = all day, the whole day

Usage notes:

In everyday speech, bütün gün is extremely common.
tüm gün is also correct and maybe sounds a little more neutral/formal to some speakers, but there’s no big meaning difference.

So you can say:

Bütün gün dışarıda kalmak istiyorum. ✅
Tüm gün dışarıda kalmak istiyorum. ✅

Is the word order fixed, or can I change it, for example using çünkü?

Turkish word order is relatively flexible, but there are preferences.

Your sentence is:

Bugün hava o kadar güzel ki bütün gün dışarıda kalmak istiyorum.

This has a cause → result flow:

Bugün hava o kadar güzel ki (cause, intensity)
bütün gün dışarıda kalmak istiyorum (result)

You could also express it using çünkü (because) and change the order:

Bütün gün dışarıda kalmak istiyorum çünkü bugün hava çok güzel.
I want to stay outside all day because the weather is very nice today.

Or:

Bugün hava o kadar güzel ki, bütün gün dışarıda kalmak istiyorum.
(just adding a comma for clarity)

But within each clause, the verb generally comes at the end:

Bugün hava o kadar güzel ki… (verb “is” is implied)
…bütün gün dışarıda kalmak istiyorum. (main verb: istiyorum)

You cannot freely move istiyorum to the middle; it must close the clause:

Bütün gün dışarıda kalmak istiyorum. ✅
Bütün gün istiyorum dışarıda kalmak. ❌

Could we leave out Bugün or hava and still have a correct sentence?

Yes, depending on what you want to say and what is clear from context.

Dropping Bugün:
- Hava o kadar güzel ki bütün gün dışarıda kalmak istiyorum.
  The weather is so nice (today/now) that I want to stay outside all day.
If the time (today/now) is already clear, Bugün can be omitted.
Dropping hava:
- Bugün o kadar güzel ki…
  This sounds incomplete: Today is so nice that…
  It can work in very informal, poetic, or context-heavy situations, but normally you keep “hava” because you are specifically talking about the weather.

So:

Bugün hava o kadar güzel ki… → natural, explicit
Hava o kadar güzel ki… → also natural, time is implicit
Bugün o kadar güzel ki… → possible for stylistic effect, but not the standard neutral way to say it about the weather.

Is there any difference between saying Bugün hava çok güzel and Bugün hava o kadar güzel ki …?

Yes, there is a difference in emphasis.

Bugün hava çok güzel.
= The weather is very nice today.
→ This is a simple statement of degree (very nice), no explicit consequence.
Bugün hava o kadar güzel ki bütün gün dışarıda kalmak istiyorum.
= The weather is so nice today that I want to stay outside all day.
→ This expresses:
- a high degree (so nice)
- plus a result (I want to stay outside all day)

So o kadar … ki is stronger and more expressive because it links the niceness of the weather to what it makes you want to do.