Jeg blir i bedre humør hver gang huset lukter rent tøy og middagen allerede står klar.

Blir means become/get, while er means am/is/are.

So:

• Jeg er i bedre humør = I am in a better mood
• Jeg blir i bedre humør = I get into a better mood / I become happier

In this sentence, the idea is that this situation causes a change in mood, so blir is the natural choice.

Literally, it means in better mood.

Norwegian often uses i humør or i godt/dårlig humør where English uses in a good/bad mood.

So:

• i humør = in the mood
• i godt humør = in a good mood
• i bedre humør = in a better mood

Notice that Norwegian does not need an article here in the same way English usually does.

Because god and related expressions use an irregular comparative:

• god = good
• bedre = better
• best = best

In this sentence, bedre is the comparative form, because the speaker is saying their mood improves.

Hver gang means every time / whenever.

It introduces a repeated situation:

• hver gang det regner = every time it rains
• hver gang hun ringer = every time she calls

In your sentence, hver gang huset lukter rent tøy og middagen allerede står klar means every time the house smells of clean laundry and dinner is already ready.

Those are the definite forms:

• hus = house

• huset = the house

• middag = dinner / the dinner / evening meal
• middagen = the dinner / dinner

Norwegian usually adds the definite article as an ending on the noun instead of putting a separate word before it.

So:

• huset = the house
• middagen = the dinner / dinner

In natural English translation, middagen is often just dinner, even though Norwegian uses the definite form.

The verb lukte can mean either:

• to smell in the sense of giving off a smell
• sometimes to smell of / smell like

So huset lukter rent tøy means the house has the smell of clean laundry.

This is very natural in Norwegian. English often needs a preposition like of:

• Det lukter kaffe = It smells like coffee
• Huset lukter rent tøy = The house smells of clean laundry

Because tøy is usually a neuter noun, and here it is being treated as an uncountable mass noun, something like laundry/clothes in a general sense.

For neuter singular or uncountable nouns, the adjective often takes -t:

• rent tøy = clean laundry / clean clothes

Compare:

• en ren skjorte = a clean shirt
• et rent håndkle = a clean towel
• rent tøy = clean laundry

You may also see rene klær when the noun is plural:

• rene klær = clean clothes

So rent tøy is correct because of the noun form and how it is being used.

Here tøy means clothes/fabric/laundry, and in this sentence it most naturally means clean laundry or freshly washed clothes.

Depending on context, tøy can refer to:

• clothing in general
• fabric/material
• laundry

In this sentence, because of lukter rent, it strongly suggests the smell of freshly washed laundry.

Står klar literally means stands ready, but in natural English it usually means is ready.

Norwegian often uses verbs like stå, ligge, and sitte in ways that are more physical or image-based than English:

• Maten står på bordet = The food is on the table
• Middagen står klar = Dinner is ready / dinner is waiting

So står klar gives a vivid sense that dinner is already prepared and there waiting.

Allerede means already, and its placement here is very normal in Norwegian.

The clause is:

• middagen allerede står klar

In subordinate clauses, adverbs like allerede, ikke, ofte, etc. often come before the finite verb.

That is an important Norwegian word-order pattern.

Compare:

• Main clause: Middagen står allerede klar
• Subordinate clause: ... at middagen allerede står klar

In your sentence, the part after hver gang behaves like a subordinate clause, so allerede before står fits well.

Because hver gang introduces a subordinate clause.

In Norwegian:

• Main clauses usually follow the verb-second rule.
• Subordinate clauses do not usually follow that same pattern.

So you get:

• Main clause: Middagen står klar
• Subordinate clause: ... hver gang middagen står klar

And with an adverb:

• Main clause: Middagen står allerede klar
• Subordinate clause: ... hver gang middagen allerede står klar

That is why the word order looks more like English here.

Yes, it is the present tense throughout:

• jeg blir
• huset lukter
• middagen står

Norwegian commonly uses the present tense for things that happen regularly or whenever a certain situation occurs.

So this sentence means something like:

• I get into a better mood every time the house smells of clean laundry and dinner is already ready.

It is not necessarily happening right now only once; it describes a repeated reaction.

Historically and in some dialects or older usage, middag could refer to the main meal of the day, which was sometimes earlier in the day. But in most modern everyday Norwegian, middag usually means dinner / the evening meal.

So in this sentence, middagen allerede står klar is best understood as dinner is already ready.

Yes, a few things are very natural Norwegian:

• bli i bedre humør = get in a better mood
• lukte rent tøy = smell of clean laundry
• middagen står klar = dinner is ready / waiting

None of these are strange or overly formal. Put together, the sentence sounds warm and domestic, describing a familiar comforting situation.