Learn Hardcore Norwegian: Jeg går ofte i skogen når himmelen er klar. - I often walk in the forest when the sky is clear.

In Norwegian, gå can mean both “to go” and “to walk.” In this sentence it means “to walk.” The simple present går expresses a habitual action: jeg går ofte i skogen = “I often walk in the forest.”

Why is the adverb ofte placed between the verb and the rest of the sentence? Can I move it?

Norwegian main clauses follow the V2 rule (finite verb in second position). Adverbs like ofte normally come right after the verb:
Subject + Verb + Adverb + Object/Complement.
– Jeg (S) går (V) ofte (Adv) i skogen.
You can also front the adverb for emphasis, but the verb must stay in position two:
– Ofte går jeg i skogen når himmelen er klar.

Why is it i skogen instead of i en skog or i skog?

Using the definite form skogen (“the forest”) here expresses you go into forests in general.
– i skogen = “in the forest” (habitual/idiomatic)
If you said i en skog, it would mean a specific forest (“in a forest”), which changes the nuance.

Do I need a comma before når himmelen er klar?

In Norwegian, commas before subordinate time clauses (introduced by når) are optional unless you want a strong pause. Most speakers omit it in simple sentences:
– Jeg går ofte i skogen når himmelen er klar.
You may write Jeg går ofte i skogen, når himmelen er klar. to signal a pause, but it’s not obligatory.

What if I start with the time clause: Når himmelen er klar? Do I change anything?

Yes. Leading with a time clause still follows V2, so you invert the subject and verb in the main clause:
– Når himmelen er klar, går jeg ofte i skogen.

Why is himmelen in the definite form? I expected en himmel.

We typically refer to “the sky” in a general sense, so we use the definite form himmelen. Saying en himmel (“a sky”) would suggest one sky among many, which isn’t how we talk about the sky over us.

Why is når used here instead of da? Both can mean “when.”

In Norwegian, når is used for repeated or general situations in present and future. da is reserved for specific past events. Since this sentence describes a habitual present action, når is correct.

Why isn’t there an article before klar in himmelen er klar?

In a copular clause (Subject + er + Adjective), you don’t insert an article before the adjective. You simply say himmelen er klar (“the sky is clear”).

In the clause når himmelen er klar, why isn’t the verb er at the end, like in German subordinate clauses?

Norwegian subordinate clauses introduced by conjunctions (such as når) follow Subject–Verb order, not verb-final. So you get:
når (conj) himmelen (S) er (V) klar.