Mesmo que o dia pareça nublado, o médico recomenda usar protetor solar na praia.

In this sentence, mesmo que means even if / even though.

• mesmo alone usually means same or even (as in intensity):

  • o mesmo dia = the same day
  • é mesmo caro = it’s really / very expensive

• que alone is normally that or which / who, introducing a clause.

When you put them together as mesmo que, it becomes a fixed expression that introduces a hypothetical or concessive clause:

• Mesmo que o dia pareça nublado, ...
  = Even if the day seems cloudy, ...
  (Concession: despite that, the recommendation still holds.)

mesmo que nearly always triggers the subjunctive afterwards in Portuguese, because it introduces something hypothetical or not fully factual.

pareça is the present subjunctive of parecer (to seem).
parece is the present indicative.

After mesmo que, Portuguese normally requires the subjunctive because we’re talking about a possible or hypothetical situation, not something we’re asserting as a fact.

• O dia parece nublado. (indicative)
  = The day seems cloudy. (speaker is stating it as an observation)

• Mesmo que o dia pareça nublado, ... (subjunctive)
  = Even if the day seems cloudy, ... (we’re not really interested in whether it does or doesn’t; it’s a condition)

So the structure is:

• mesmo que
  • subjunctive
    → Mesmo que o dia pareça nublado, ...

Using parece here would sound ungrammatical to a native speaker.

Not in standard European Portuguese.

1. mesmo se is possible but far less common than mesmo que, and when it is used, it usually takes the future subjunctive or the present subjunctive, not the indicative:

   • Mesmo se o dia parecer nublado, ... (future subjunctive)
   • Mesmo se o dia pareça nublado, ... (present subjunctive, less usual with se)

2. se + presente do indicativo (se o dia parece) is not used for this kind of hypothetical / concessive idea. It sounds wrong.

Natural options would be:

• Mesmo que o dia pareça nublado, ... ✅ (most natural)
• Mesmo se o dia parecer nublado, ... ✅ (possible but less common, and slightly different feel)

So Mesmo se o dia parece nublado ❌ is not correct.

Both are grammatically possible, but there’s a nuance:

• parecer nublado = to seem / look cloudy
  → focuses on appearance (what it looks like to you)

• estar nublado = to be cloudy
  → states the actual weather condition

So:

• Mesmo que o dia pareça nublado, ...
  = Even if the day looks cloudy (to you), ...

• Mesmo que o dia esteja nublado, ...
  = Even if the day is (actually) cloudy, ...

In everyday speech, both would be understood similarly. The original just highlights the subjective impression rather than an objective meteorological fact.

In Portuguese, recomendar does not take a preposition before a verb in the infinitive:

• recomendar + infinitivo:
  
  • O médico recomenda usar protetor solar. ✅
  • O médico recomenda fazer exercício. ✅

Forms like:

• recomenda de usar ❌
• recomenda a usar ❌

are ungrammatical.

If you want a different structure, you can use:

• recomendar que + subjuntivo:
  
  • O médico recomenda que uses protetor solar. (to you, informal singular, PT-PT)
  • O médico recomenda que se use protetor solar. (impersonal / general)

But with an infinitive, you say recomenda usar, with no preposition.

Both can express essentially the same idea, but they differ in form and focus:

1. recomenda usar protetor solar

   • Structure: recomendar + infinitive
   • More direct, neutral, and common when the subject of both verbs is the same or general:
     • O médico recomenda usar protetor solar na praia.
       → The doctor recommends using sunscreen at the beach.
       (General advice: people in general should do this.)

2. recomenda que se use protetor solar

   • Structure: recomendar que + subjunctive
   • More explicitly impersonal/formal. se use = impersonal passive-like construction, “that sunscreen be used”:
     • O médico recomenda que se use protetor solar na praia.
       → The doctor recommends that sunscreen be used at the beach.

In everyday speech, recomenda usar is simpler and very common; recomenda que se use sounds a bit more formal or written. Both are correct.

In Portuguese, when talking about something in a general, non-specific way (especially after certain verbs like usar, comer, beber, comprar in a generic sense), you often omit the article:

• usar protetor solar = to use sunscreen (in general)
• usar chapéu = to wear a hat (as a habit / in general)
• comer carne = to eat meat

If you say:

• usar o protetor solar
  it tends to sound like you mean a specific sunscreen already known in the context (e.g., the one you bought, the one the doctor gave you), not sunscreen in general.

Here, the idea is a general recommendation, so usar protetor solar without the article is natural.

In contemporary Portuguese (Portugal), both spellings exist, but the official spelling according to the Portuguese Language Orthographic Agreement (Acordo Ortográfico) is:

• protetor solar (without c)

Before the reform, European Portuguese used protector, and you may still see protector solar in older texts or from people who prefer the old spelling.

In modern, standard writing (schools, official documents, most newspapers), you’ll usually see protetor solar.
In speech, of course, there’s no difference.

na is simply the contraction of em + a:

• em + a praia → na praia

Portuguese almost always contracts these in writing and speech:

• em + o → no (no carro)
• em + a → na (na praia)
• em + os → nos (nos restaurantes)
• em + as → nas (nas lojas)

à praia is a + a praia (with crase), and it usually indicates movement towards a place:

• Vou à praia. = I’m going to the beach.

In your sentence, the idea is location (at the beach), not movement to the beach, so na praia (“at the beach / on the beach”) is correct.
em a praia without contracting is simply not used in normal Portuguese.

It can correspond to both English at the beach and on the beach, depending on context. In Portuguese:

• na praia is the general expression for being in the beach area, not necessarily physically touching the sand.

So in this sentence:

• usar protetor solar na praia
  → means to use sunscreen at the beach / on the beach, in the general sense of “when you’re spending time at the beach.”

Portuguese doesn’t need to distinguish at vs on here; na praia comfortably covers both.

Yes. It’s possible and grammatical, though the rhythm changes a bit:

• Mesmo que o dia pareça nublado, o médico recomenda usar protetor solar na praia.
• O médico recomenda usar protetor solar na praia, mesmo que o dia pareça nublado.

Both are fine in European Portuguese.
Starting with Mesmo que... slightly emphasises the condition; putting it at the end feels a bit like an afterthought added to the main statement.

Mesmo que is perfectly natural in everyday spoken Portuguese and is not restricted to formal contexts. You can use it in speech and writing.

Close alternatives include:

• Embora o dia pareça nublado, ...
  = Although the day seems cloudy, ...

• Ainda que o dia pareça nublado, ...
  = Even though / although the day seems cloudy, ...
  (a bit more formal/literary)

Of these, mesmo que and embora are the most common in everyday European Portuguese.

Yes, those are also common, with slightly different nuances:

• usar protetor solar
  → to use sunscreen (broad, neutral, covers the whole idea: having it on / applying it)

• pôr protetor solar
  → literally to put on sunscreen (focus on the act of putting it on)

• passar protetor solar
  → literally to spread / rub on sunscreen (very common colloquially)

Examples:

• O médico recomenda pôr protetor solar na praia.
• O médico recomenda passar protetor solar na praia.

All three are acceptable in Portugal; usar protetor solar feels slightly more neutral and general, which is why it works nicely in your sentence.