Learn Hardcore Norwegian: Temperaturen er lav i kveld.

It means this evening/tonight (the evening of today). It refers to the period from early evening until night. It’s not used for late night; that would be i natt.

Why is it temperaturen and not just temperatur?

Norwegian marks definiteness with a suffix:

Masculine: en temperatur (a temperature) → temperaturen (the temperature) You’re talking about a specific, known temperature (the current one), so the definite form temperaturen is natural. Using bare temperatur here would sound odd.

Could I say Det er lav temperatur i kveld instead?

Yes, that’s grammatical and means “There is low temperature tonight,” but it sounds a bit technical/formal. In everyday speech you’d more often say:

Temperaturen er lav i kveld.
Or even more idiomatically about weather: Det er kaldt i kveld. (It’s cold tonight.)

Why is it lav and not lavt or lave?

This is a predicative adjective (after the verb er). Agreement rules:

Common gender singular (most nouns, including temperatur): base form → lav
Neuter singular: add -t → lavt (e.g., Nivået er lavt “The level is low”)
Plural: add -e → lave (e.g., Temperaturene er lave “The temperatures are low”) Note: lavt can also be an adverb meaning “quietly/low” (e.g., snakker lavt “speaks quietly”).

Where does i kveld go in the sentence? Can I move it?

Yes. Typical options:

Neutral: Temperaturen er lav i kveld.
Fronted time (more emphasis on when): I kveld er temperaturen lav. When you front an element like i kveld, Norwegian keeps the verb in second position: I kveld er … (V2 word order).

How do I make this a yes/no question?

Invert subject and verb:

Er temperaturen lav i kveld? (Is the temperature low tonight?)

How do I negate it?

Place ikke after the finite verb:

Temperaturen er ikke lav i kveld. With fronting: I kveld er temperaturen ikke lav.

How do I pronounce the words?

temperaturen: roughly “tem-peh-rah-TOO-ren” (main stress on the “-tur-” part)
lav: “lahv” (long a)
i kveld: “ee kvel” (the d in kveld is silent in many accents) Norwegian v is like English v; i is a clear long “ee.”

What gender is temperatur, and how do I inflect it?

Masculine in Bokmål:

Singular: en temperatur → temperaturen
Plural: temperaturer → temperaturene

Why use lav (low) and not kald (cold)?

Both can be correct, but they do different things:

lav states the level is low (more neutral/technical: temperature, speed, level).
kald describes the sensation/weather. For everyday talk about weather, Det er kaldt i kveld is very natural.

Why not i kvelden? What about på/om kvelden?

Specific time today: i kveld (this evening/tonight)
Habitual/general: om kvelden or på kvelden (in the evenings) So you say i kveld, not i kvelden, for tonight.

Can I talk about the future/forecast?

Yes. Use blir (becomes/will be):

Temperaturen blir lav i kveld. (The temperature will be low tonight.) You can also say kommer til å være, but blir is shorter and common in forecasts.

Is there a difference in Nynorsk?

Yes, the adjective is typically låg in Nynorsk:

Temperaturen er låg i kveld. (Nynorsk) In Bokmål (the sentence you have), lav is standard.

Is it ever written as one word, ikveld?

Standard Bokmål is two words: i kveld. The one-word form may appear in informal texting or older writing but isn’t standard.