Köd van.

Yes, Hungarian often leaves out the present-tense form of to be in sentences like:

• A ház nagy. = The house is big.
• Ő tanár. = He/She is a teacher.

But Köd van. is different. Here van does not just link two things like English is. It expresses existence/presence, more like there is in English.

So:

• Köd van. = literally Fog is / There is fog
• not a simple X is Y sentence

That is why van stays.

In Hungarian, general weather or environmental conditions often appear without an article.

So Köd van. means There is fog / It is foggy, not There is a specific fog.

Using an article here would usually sound unnatural in this basic weather statement. Hungarian often treats these as general conditions:

• Hideg van. = It is cold.
• Meleg van. = It is warm.
• Szél van. = It is windy / There is wind.
• Köd van. = It is foggy / There is fog.

No. Hungarian does not need a dummy subject like English it in weather expressions.

English says:

• It is raining.
• It is cold.
• It is foggy.

But Hungarian can simply say:

• Esik.
• Hideg van.
• Köd van.

So there is no hidden word here meaning it. Hungarian just states the condition directly.

Köd is a noun meaning fog. In Köd van, it names the condition that exists.

A useful way to think about the structure is:

• köd = fog
• van = there is / exists

So the sentence is structurally close to There is fog.

Even though natural English may prefer It is foggy, Hungarian is using a noun-based expression here.

Yes. Ködös az idő is also correct, and it means The weather is foggy.

The difference is mainly in how the idea is expressed:

• Köd van. = There is fog / It is foggy
• Ködös az idő. = The weather is foggy

The first is very direct and common. The second explicitly mentions the weather (az idő) and uses the adjective ködös (foggy).

• köd = fog (noun)
• ködös = foggy (adjective)

So:

• Köd van. = There is fog
• Ködös az út. = The road is foggy / fog-covered
• Ködös az idő. = The weather is foggy

English often prefers an adjective like foggy, but Hungarian can very naturally use the noun phrase Köd van.

A simple learner-friendly pronunciation guide is:

• köd ≈ kuerd with a short clipped ending
• van ≈ vawn or vahn, depending on accent habits

The most important sound here is ö.

About ö

Hungarian ö is like a short version of the vowel in German schön or French peu.
It is not like English o in go.

Stress

Hungarian stress is always on the first syllable of each word:

• KÖD
• VAN

So: KÖD van

Yes, but Köd van. is the normal neutral order.

Hungarian word order is flexible, but changes often affect focus or emphasis. In a simple statement about the weather, Köd van is the natural choice.

You may hear altered word order in special contexts, but for learners, the safest standard form is:

• Köd van.

The usual negative form is:

• Nincs köd. = There is no fog.

Hungarian uses nincs as the negative of van in existence statements like this.

So not:

• Köd nem van. ✘

but:

• Nincs köd. ✔

This is very common with existential sentences:

• Van víz. = There is water.
• Nincs víz. = There is no water.

You can change van just like other forms of to be:

• Köd volt. = There was fog / It was foggy.
• Köd lesz. = There will be fog / It will be foggy.

This same pattern works with many similar weather expressions:

• Hideg volt. = It was cold.
• Meleg lesz. = It will be warm.

Yes, very much so. It sounds natural and idiomatic.

Hungarian often describes weather and environmental conditions with this pattern:

• Hideg van. = It is cold.
• Meleg van. = It is warm.
• Sötét van. = It is dark.
• Köd van. = It is foggy / There is fog.

So this is a useful pattern to learn, not just an isolated sentence.