Learn Hardcore Norwegian: Klærne er så våte at tørketrommelen må gå to ganger. - The clothes are so wet that the dryer has to run twice.

Klærne means “the clothes” (definite plural).
Klær is “clothes” without the definite article (indefinite plural).
Norwegian often uses the definite form where English uses “the,” especially when a specific, known set is meant. Here, it’s those particular clothes you’ve washed, so klærne fits best.
Indefinite would sound general: Klær er så våte at … = “Clothes are so wet that …” (odd as a general statement).

Why is the adjective våte and not våt or vått?

Adjectives in predicative position agree with the subject:

Masculine/feminine singular: våt (Boka er våt.)
Neuter singular: vått (Huset er vått.)
Plural: våte (Klærne er våte.) Since klærne is plural, you use våte.

What does the pattern så … at do here?

It introduces a result clause: “so … that …”

Klærne er så våte at … = “The clothes are so wet that … (result)”
Don’t confuse with comparison så … som (“as … as”): e.g., så våt som = “as wet as.”

Is the word order inside the at-clause correct: at tørketrommelen må gå …?

Yes. In subordinate clauses, the subject comes before the finite verb:

at [subject] [finite verb] … → at tørketrommelen må gå … If you add a negation, it goes before the finite verb in a subordinate clause:
at tørketrommelen ikke må gå … In a main clause it’s different (V2): Tørketrommelen må ikke gå …

Why is it tørketrommelen (definite) and not just tørketrommel?

Tørketrommelen = “the dryer,” the one you’re using or referring to in context.
En tørketrommel = “a dryer” (indefinite).
Using the definite form is natural when the reference is specific. An indefinite here would sound like a generic statement about dryers.

What does gå mean with machines? Does it literally mean “go”?

With machines, gå commonly means “run/work/be in operation.”

Tørketrommelen går. = “The dryer is running.” Other natural options:
kjøre (noen kjører noe): Vi må kjøre tørketrommelen to ganger. (“We have to run the dryer twice.”)
Passive: Tørketrommelen må kjøres to ganger.
sette på: Vi må sette på tørketrommelen to ganger. (“turn it on/run it twice.”)

Why is it må gå and not må å gå?

Norwegian modal verbs take a bare infinitive (no å):

må gå, kan gå, skal gå, vil gå, bør gå Compare non-modals that do take å: trenger å gå, prøver å gå.

What’s the difference between to ganger, en gang til, and to ganger til?

to ganger = “twice.”
en gang til = “one more time/again.”
to ganger til = “two more times.” So your sentence says the dryer must run twice total. If you mean it has already run once and needs one more, say en gang til. If it needs two more beyond what’s already been done, say to ganger til.

Could I use for våte instead of så våte?

No. for + adjective means “too” (excessive), not “so”:

Klærne er for våte = “The clothes are too wet.”
Klærne er så våte at … = “The clothes are so wet that …” (result)

Do I need a comma before at?

No. In a sentence like this, you typically do not use a comma before at. The given punctuation is standard: Klærne er så våte at …

Can I replace tørketrommelen with a pronoun like den in the at-clause?

Only if the antecedent is clear and matches in number/gender. In this exact sentence, using den would be risky because the only prior noun is plural (klærne). Safer choices:

Repeat the noun: … at tørketrommelen må gå …
Or establish the dryer first, then use den later when it’s unambiguous.

Is klær always plural? How do I say “a piece of clothing”?

Klær is plural-only (“clothes”).
For one item: et klesplagg or simply et plagg (“a garment”).
Related forms in compounds: kles- (e.g., klesvask = “laundry”).

Any traps with må I should know (like negation)?

Yes:

må = “must/has to” (necessity) or sometimes “must” (deduction): Du må være trøtt. (“You must be tired.”)
må ikke = “must not” (prohibited), not “don’t have to.”
“Don’t have to” is trenger ikke: Du trenger ikke å gå. Tense forms: present må, preterite måtte, perfect har måttet.

Pronunciation tips for key words?

klærne: long æ; in Eastern Norwegian, rn tends to merge into a retroflex sound.
våte: å like the vowel in English “law,” but shorter/rounder.
tørketrommelen: stress on the first syllable of each part: TØR-ke-TROM-mel-en; clear trilled or tapped r.
ganger: hard g; both g’s are pronounced.