En el sur hace más calor, pero el oeste de la península me parece más verde que el este.

En el sur means in the south / in the southern part.

Here the sentence is talking about a region as an area: In the south, it’s hotter.

By contrast, al sur often means to the south or south of something, especially when there is a reference point:

• Al sur de Madrid = to the south of Madrid

So in this sentence, en el sur is the natural choice because it means in the southern part of the peninsula.

For weather, Spanish usually uses hacer + a weather noun:

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

So hace más calor literally looks like it makes more heat, but in natural English it means it’s hotter.

Es caliente is generally not how Spanish talks about weather. Also, caliente often means that something itself is hot to the touch, or in some contexts can sound awkward or suggestive. For climate and temperature in general, hace calor is the standard expression.

Más calor means more heat, but in this kind of sentence it is simply the normal way to say hotter.

So:

• En el sur hace calor. = It’s hot in the south.
• En el sur hace más calor. = It’s hotter in the south.

Spanish often expresses comparisons with más + noun rather than changing the adjective the way English sometimes does.

In Spanish, compass directions are often treated as nouns, so they commonly take the definite article:

• el sur = the south
• el norte = the north
• el este = the east
• el oeste = the west

That is why the sentence says:

• en el sur
• el oeste de la península
• el este

This is very normal Spanish. English also sometimes does this: the south, the west, etc.

De la península specifies what west we are talking about: the west of the peninsula.

Without that phrase, el oeste could sound less specific. The full phrase makes it clear that the speaker means the western part of the peninsula.

In context, la península usually refers to the Iberian Peninsula.

Me parece means it seems to me or it looks to me.

So:

• El oeste de la península me parece más verde... = The west of the peninsula seems greener to me...

The me means to me.

This expression is useful because it softens the statement. The speaker is not saying it is an absolute fact, but rather giving a personal impression.

Spanish normally uses an indirect object pronoun with parecer when saying who something seems to:

• me parece = it seems to me
• te parece = it seems to you
• le parece = it seems to him/her/you formal

You can add a mí for emphasis:

• A mí me parece más verde.

But the pronoun me is the basic form you need. Using only parece a mí would not be the normal structure here.

Spanish makes comparisons with:

• más + adjective + que

So:

• más verde que = greener than

In the sentence:

• el oeste ... me parece más verde que el este = the west seems greener to me than the east

The word que is the standard word for than in this kind of comparison.

Because Spanish can leave out repeated information when it is already understood.

So:

• el oeste de la península me parece más verde que el este

really means:

• the west of the peninsula seems greener to me than the east of the peninsula

But repeating de la península would be unnecessary, so Spanish leaves it out. English does the same thing very often.

Verde describes el oeste, which is singular:

• el oeste ... más verde

Then el este is also singular, so the comparison is between two singular regions.

Also, verde has the same form for masculine and feminine in the singular:

• verde
• verde

Only the plural changes:

• verdes

So here verde is exactly the form you would expect.

Yes, but the meaning would be stronger.

• El oeste de la península es más verde que el este. = The west of the peninsula is greener than the east.

This sounds more like a direct statement of fact.

• El oeste de la península me parece más verde que el este. = The west of the peninsula seems greener to me than the east.

This sounds more personal and subjective: in my opinion / from my point of view.

Pero means but and connects two contrasting ideas:

• In the south it’s hotter
• but the west seems greener than the east

The speaker is comparing different parts of the peninsula and contrasting two observations: temperature in the south and vegetation/landscape in the west versus east.

Normally, no. In Spanish, compass directions are usually written in lowercase:

• sur
• este
• oeste
• norte

So the sentence is correctly written with lowercase letters.

They would only be capitalized in special cases, such as at the beginning of a sentence or in some proper names.

In this context, it most likely refers to the Iberian Peninsula, especially in Spain-focused Spanish.

That includes Spain and Portugal, and geographically also Andorra and Gibraltar. In everyday Spanish from Spain, la península often means mainland Iberia, especially when contrasting it with islands such as the Balearic or Canary Islands.

So the sentence is probably talking about regional differences within the Iberian Peninsula.