Si fa sol demà, vull estendre la roba al balcó i no posar-la a la secadora.

In Catalan, weather is often expressed with fer (to make / to do) in set expressions.

So:

• fa sol = it’s sunny
• fa fred = it’s cold
• fa calor = it’s hot
• fa vent = it’s windy

This is just the normal idiomatic way to talk about weather. A literal word-for-word translation into English does not work well here.

After si meaning if, Catalan normally uses the present tense to talk about future conditions, just like English often does:

• If it’s sunny tomorrow, ...
• Catalan: Si fa sol demà, ...

So fa is present tense, but the meaning is future because demà already makes the time clear.

Using futur after si in this kind of condition is generally not standard Catalan.

Vull is the 1st person singular of voler (to want):

• vull = I want

Catalan often uses the present tense here naturally, even when talking about a plan for tomorrow:

• Si fa sol demà, vull estendre la roba...
• If it’s sunny tomorrow, I want to hang the clothes...

In real life, this can sound like a present wish or intention. Depending on context, Catalan might also use other forms for future intention, but vull is perfectly natural if the speaker is expressing what they want to do.

Estendre literally means to spread out or to hang out. With laundry, it is the normal verb for hanging clothes up to dry.

So:

• estendre la roba = to hang out the washing / laundry

This is more idiomatic than translating English hang the clothes word for word.

In Catalan, roba is a singular collective noun that often means clothes or laundry as a group.

So:

• la roba = the clothes / the laundry

Even though English often uses a plural word, Catalan uses the singular noun roba.

Because a + el contracts in Catalan:

• a + el = al

So:

• al balcó = to/on the balcony

This is very common:

• al carrer = to the street
• al cotxe = to the car

-la is a direct object pronoun meaning it, and it refers back to la roba.

So:

• posar-la = to put it
• here, it = the laundry / the clothes

Catalan often avoids repeating the noun and uses a pronoun instead, just like English does:

• hang the laundry on the balcony and not put it in the dryer

Because roba is grammatically feminine singular, the pronoun is la.

In Catalan, object pronouns are often attached to an infinitive, gerund, or affirmative command.

So:

• posar-la = to put it
• estendre-la = to hang it out
• fer-ho = to do it

The hyphen is the normal written form when the pronoun is attached to the infinitive.

When a pronoun goes with an infinitive, it is normally attached to that infinitive:

• no posar-la = not to put it

So in this sentence, the correct structure is:

• vull estendre la roba ... i no posar-la a la secadora

That is because both estendre and posar-la depend on vull.

Because Catalan, like English, can use one main verb with two coordinated infinitives.

Here the structure is:

• vull
  • estendre la roba al balcó
• i
  • (vull) no posar-la a la secadora

The second vull is understood, so it does not need to be repeated.

In English we do the same:

• I want to hang the laundry outside and not put it in the dryer.

Balcó simply means balcony. In this sentence, estendre la roba al balcó means hanging laundry out on the balcony to dry.

So the phrase is very natural in Catalan-speaking places where people often dry clothes outdoors.

Yes. Secadora is the normal Catalan word for a dryer or tumble dryer.

So:

• a la secadora = in the dryer

The preposition a is used here because you are putting the clothes into that appliance.

Because demà by itself normally means tomorrow.

So:

• demà = tomorrow

Catalan usually does not need an article here, just as English does not say the tomorrow.

No. They are different words.

• si = if
• sí = yes

The accent matters. In your sentence:

• Si fa sol demà... = If it’s sunny tomorrow...

Without the accent, it is the conjunction if.

Yes. In this context, la roba is very naturally understood as the laundry / the washing.

Because the sentence mentions:

• estendre
• balcó
• secadora

all of that clearly points to clothes that have been washed and are being dried. So la roba here is best understood as the laundry.

Yes. Si demà fa sol is also correct.

Both are natural:

• Si fa sol demà
• Si demà fa sol

The difference is mostly one of emphasis or rhythm, not meaning. Catalan often allows this kind of flexibility in adverb placement.