Hoy hace sol, así que quiero caminar por la playa.

Because Spanish often uses hacer + weather noun for weather expressions.

So:

• hace sol = it’s sunny
• hace calor = it’s hot
• hace frío = it’s cold
• hace viento = it’s windy

Even though hacer usually means to do or to make, in weather expressions the whole phrase works idiomatically. A learner should understand hace sol as one chunk, not word by word.

Spanish often uses impersonal weather expressions, so there is no real subject like English it.

In English, you say it’s sunny, but that it does not really refer to anything specific. Spanish simply leaves that kind of dummy subject out. That is why hace stays in the third person singular form.

So hace sol is just the normal Spanish way to say it’s sunny.

Así que means so, therefore, or as a result.

It connects a cause to a result:

• Hoy hace sol, así que quiero caminar por la playa.
• Today it’s sunny, so I want to walk along the beach.

It is a very common and natural connector in everyday Spanish.

They do different jobs:

• porque gives the reason
• así que gives the result

Compare:

• Quiero caminar por la playa porque hoy hace sol.
  I want to walk along the beach because it’s sunny today.

• Hoy hace sol, así que quiero caminar por la playa.
  It’s sunny today, so I want to walk along the beach.

Both are correct, but the focus changes depending on which part comes first.

Because Spanish usually omits subject pronouns when they are not needed.

The verb quiero already tells you the subject is I:

• quiero = I want

So yo is optional. You would normally add yo only for emphasis, contrast, or clarity.

For example:

• Yo quiero caminar, pero él no.
  I want to walk, but he doesn’t.

In your sentence, quiero by itself is perfectly natural.

Because por and a express different ideas.

• caminar a la playa = to walk to the beach
  This focuses on the destination.

• caminar por la playa = to walk along the beach / around the beach area
  This focuses on movement within that place.

So in your sentence, por la playa suggests being at the beach and walking along it, not going there.

Yes, you could, but it feels slightly different.

• caminar en la playa = walk on the beach
• caminar por la playa = walk along or around the beach area

Both can be natural, but por la playa often gives a stronger sense of movement through the place. In a sentence like this, it sounds very natural.

Because Spanish uses the definite article with nouns like this much more often than English does.

So Spanish naturally says:

• ir a la playa
• estar en la playa
• caminar por la playa

In English, learners sometimes want to drop the, but in Spanish la playa is the normal form here.

Hoy is a time adverb, and Spanish can place it in different parts of the sentence. Putting it first is very common because it sets the time frame immediately.

• Hoy hace sol = neutral and very natural
• Hace sol hoy = also possible, but can sound more marked depending on context

So the sentence begins with hoy because it is a natural way to set the scene: today.

The accent mark shows the correct stress: a-SÍ.

Without the accent, asi would be incorrect in standard Spanish spelling. Accent marks in Spanish are important because they often tell you which syllable to stress and can sometimes distinguish between words.

So here, así must be written with the accent.

Because the sentence is joining two complete ideas:

• Hoy hace sol
• así que quiero caminar por la playa

In Spanish, it is very common to put a comma before a connector like así que when it introduces the result of the first clause. It makes the sentence clearer and more natural in writing.

Yes. Both are possible, but they are not exactly the same.

• caminar = to walk
• pasear = to stroll / to go for a walk

Pasear often sounds a bit more leisurely or relaxed. Since walking on the beach is often a pleasant activity, pasear por la playa would also sound very natural.

Your original sentence with caminar is still completely correct. It is just a bit more neutral and direct.