Learn Hardcore Danish: Vi mødes indenfor i salen, når vejret er for koldt udenfor. - We meet inside in the hall when the weather is too cold outside.

The -s on mødes is related to the passive ending in Danish, but with some verbs (like mødes, skilles, ses) it often has this reciprocal meaning:

Vi ses = See you / we’ll see each other.
Vi mødes kl. 8 = We’ll meet (each other) at 8.

Here, Vi møder indenfor i salen would sound more like We happen to meet (someone) inside in the hall, without the clear idea that the people in vi are all meeting each other by arrangement.

Could I say Vi møder hinanden i salen instead of Vi mødes i salen?

Yes, grammatically you can:

Vi mødes i salen.
Vi møder hinanden i salen.

Both mean roughly We meet each other in the hall.

Nuance:

Vi mødes is the most natural and common way to talk about an arranged meeting.
Vi møder hinanden is correct, but often used more for bumping into each other or simply stating that two people meet. In everyday Danish, people overwhelmingly prefer mødes for planned meetups.

So in this sentence, Vi mødes indenfor i salen sounds more idiomatic than Vi møder hinanden indenfor i salen.

Why is når used here and not hvis or da?

Danish makes a clear distinction:

når = when for repeated / general / future situations
da = when for a single event in the past
hvis = if, for conditions / possibilities

In your sentence:

når vejret er for koldt udenfor
= when the weather is too cold outside (every time that happens)

So:

Når vejret er for koldt udenfor, mødes vi indenfor i salen.
= Every time the weather is too cold, we meet inside.

Comparisons:

Hvis vejret er for koldt, bliver vi hjemme.
If the weather is too cold, we stay at home. (a condition)
Da vejret var for koldt, mødtes vi indenfor i salen.
When the weather was too cold, we met inside in the hall. (one specific past situation)

Here we’re talking about a general rule/habit, so når is the right choice.

Why is there a comma before når?

The når‑clause is a subordinate clause (a dependent clause), and traditional Danish punctuation puts a comma before such clauses:

Vi mødes indenfor i salen, når vejret er for koldt udenfor.

Since a reform, it is technically allowed to omit that comma (the so‑called new comma), but many people and most teaching materials still use the “grammar comma”:

With comma (traditional / very common):
Vi mødes indenfor i salen, når vejret er for koldt udenfor.
Without comma (also correct with the new rules):
Vi mødes indenfor i salen når vejret er for koldt udenfor.

So the comma is there because når vejret er for koldt udenfor is a subordinate clause specifying when you meet.

Why is it vejret and not just vejr?

Vejr is the base noun “weather”, but when you talk about the weather in general, Danish almost always uses the definite form:

vejret = the weather

Examples:

Hvordan er vejret? – How is the weather?
Vejret er dårligt i dag. – The weather is bad today.

In your sentence:

når vejret er for koldt udenfor
literally: when the weather is too cold outside

Using bare vejr would sound wrong here. The natural form in almost all everyday contexts is vejret.

What does for mean in for koldt?

In this context, for means “too” (too much):

for koldt = too cold
for varmt = too warm / too hot
for dyrt = too expensive

So:

når vejret er for koldt udenfor
= when the weather is too cold outside

If you said just vejret er koldt, it would be the weather is cold (neutral description). By adding for, you say it is too cold for what you want to do (e.g. to meet outside).

Why do we have both indenfor and i salen, and then udenfor? Isn’t that redundant?

It is a bit redundant, but it’s natural Danish and adds emphasis and clarity.

indenfor = inside (as opposed to outside)
i salen = in the hall (a specific indoor place)

Together:

Vi mødes indenfor i salen
stresses that:
1. you are inside, not outside, and
2. the specific place inside is the hall.

Likewise, udenfor reinforces that it’s the outside weather that is too cold:

når vejret er for koldt udenfor
= when the weather is too cold outside (as opposed to just “the weather” in some abstract sense)

You could say in a slightly less emphatic way:

Vi mødes i salen, når vejret er for koldt.

That’s fully correct and natural too. The original just underlines the contrast indenfor ↔ udenfor.

What is the difference between inde / indenfor and ude / udenfor?

Roughly:

inde = in(side) – more neutral, just “in”
indenfor = inside (the boundary) – clearer contrast to outside, often a bit more spatial/physical

Similarly:

ude = out(side) – more neutral
udenfor = outside (the boundary) – stronger contrast, often “on the other side of a limit”

Examples:

Han er inde. – He is in(side).
Han er indenfor. – He is inside (as opposed to outside).
Hun er ude. – She is out(side).
Hun er udenfor. – She is outside (not inside the building / room / area).

In your sentence, indenfor … udenfor makes the contrast very clear:
We meet *inside in the hall, when the weather is too cold outside.*

Can I move the når‑clause to the beginning of the sentence?

Yes. Danish allows you to put the time clause first, but then the main clause must still follow V2 word order (the verb in second position):

Når vejret er for koldt udenfor, mødes vi indenfor i salen.

Word order patterns:

Main clause default:
Vi (subject) mødes (verb) indenfor i salen (rest).
If you put the når‑clause first, that entire clause counts as position 1, so the verb comes next in the main clause:
Når vejret er for koldt udenfor, mødes (verb) vi (subject) indenfor i salen.

Both orders are correct:

Vi mødes indenfor i salen, når vejret er for koldt udenfor.
Når vejret er for koldt udenfor, mødes vi indenfor i salen.

The second version just emphasizes the condition når vejret er for koldt udenfor more strongly.

What exactly does sal / salen mean here, and how is it different from other words like rum or stue?

Sal generally means a hall or large room, often used for gatherings:

sal = hall / large room
salen = the hall (definite form)

It’s typically:

a gym hall,
a concert or assembly hall,
a big meeting room in a school, town hall, etc.

Compared with other words:

rum = room (very general, any room)
værelse = room, usually a bedroom or private room
stue = living room (in a home)
lokale = room / classroom / office room (functional, often smaller than a sal)

So i salen suggests a big indoor space where several people can meet, which fits well with the idea in the sentence.