Learn Hardcore Spanish (Spain): Hoy el cielo está cubierto de nubes.

Hoy el cielo está…
Puts more emphasis on today: Today, the sky is covered with clouds (as opposed to other days).
El cielo hoy está…
Feels very neutral. Common in speech. Emphasis is slightly more on el cielo (the sky today, not something else).
El cielo está… hoy.
Also correct, but hoy at the very end is a bit less common here; it may sound slightly more "tagged on" in casual speech.

In everyday Spanish from Spain, Hoy el cielo está… and El cielo hoy está… are the most natural-sounding versions.

Why do we say Hoy and not Este día for “today”?

Spanish almost always uses hoy for “today” in everyday speech:

Hoy el cielo está cubierto de nubes.

Este día literally means this day, but it’s used much less, and usually:

in more formal or literary style
when contrasting with other days (e.g. Este día fue especial. – This day was special.)

You would not normally say Este día el cielo está cubierto de nubes in casual conversation. It sounds strange or poetic. Use hoy to talk about today’s weather.

Why is it el cielo and not just cielo? Can I drop the article?

In Spanish, singular countable nouns generally need an article (el, la, un, etc.) when they’re used in a specific sense.

El cielo is “the sky” (the specific sky we all see). In weather descriptions, Spanish usually keeps the article:

El cielo está azul. – The sky is blue.
El cielo está nublado. – The sky is cloudy.

Saying just cielo está cubierto de nubes (without el) is ungrammatical in standard Spanish.

You can omit the article in some fixed expressions (e.g. Cielo santo – Good heavens!) but not in this descriptive sentence. So you need el cielo here.

Why is it está (from estar) and not es (from ser)?

Spanish uses estar for temporary states and changing conditions, including weather and appearance at a given moment.

El cielo está cubierto de nubes.
The sky is (right now) covered with clouds; it can change later.

If you used es here (El cielo es cubierto de nubes), it would be wrong. Ser with this kind of participle doesn’t express a current state; it’s usually used for passive constructions with an agent:

El cuadro fue cubierto por una tela. – The painting was covered by a cloth.

For weather descriptions (sunny, cloudy, clear, etc.), always use estar:

Está nublado. – It’s cloudy.
El cielo está despejado. – The sky is clear.

What exactly is cubierto here? Is it a verb, an adjective, or something else?

Cubierto is a past participle of the verb cubrir (to cover). In this sentence, it behaves like an adjective describing the sky’s state:

Verb: cubrir – to cover
Past participle: cubierto – covered
Adjective use: El cielo está cubierto. – The sky is covered.

Grammatically:

está = a form of estar (linking verb)
cubierto = adjective (past participle used as an adjective) agreeing in gender and number with cielo

If the noun were feminine plural, you’d change it:

Las montañas están cubiertas de nieve. – The mountains are covered with snow.

Here, cielo is masculine singular, so you use cubierto (masculine singular).

Why is it cubierto de nubes and not cubierto por nubes?

Both de and por can appear after past participles, but they don’t feel the same here.

cubierto de nubes is the standard, idiomatic way to say “covered with clouds” as a description of appearance or content.
cubierto por nubes sounds more like an agent in a passive construction (covered by clouds as if the clouds are acting like agents). It’s grammatically possible, but it’s not the usual collocation for weather.

In Spanish, for many “covered with X” descriptions, de is normal:

cubierto de nieve – covered with snow
cubierto de polvo – covered with dust
cubierto de flores – covered with flowers

So cubierto de nubes is the natural choice here.

Could I leave out de nubes and just say Hoy el cielo está cubierto?

Yes, you can. Hoy el cielo está cubierto is perfectly natural, especially in weather or casual conversation.

Hoy el cielo está cubierto. – Today the sky is overcast / completely cloudy.

In fact, in many weather reports or everyday comments in Spain, people simply say:

Está cubierto. – It’s overcast.
El cielo está muy cubierto. – The sky is very overcast.

Adding de nubes just makes it more explicit that it’s covered with clouds, but the idea is already clear in context, so it’s often omitted.

What’s the difference between está cubierto de nubes and está nublado?

Both describe cloudy weather, but there’s a nuance:

Está nublado.
General statement: It’s cloudy. Could be somewhat cloudy or quite cloudy.
El cielo está cubierto de nubes. / El cielo está cubierto.
Stronger idea of being fully or almost fully covered with clouds – like overcast.

In practice:

If you just want to say “It’s cloudy,” Está nublado is common and simple.
If the sky is basically all grey with clouds, El cielo está cubierto (de nubes) is very natural in Spain and sounds a bit more specific.

Why is it nubes without an article (no las)? When would I use las nubes?

Here we say nubes (no article) because we’re talking about clouds in a non-specific, general way:

El cielo está cubierto de nubes.
The sky is covered with clouds (in general).

Spanish often omits the article after certain prepositions when you mean a substance or indefinite amount:

cubierto de nieve – covered with snow
lleno de agua – full of water
cubierto de nubes – covered with clouds

You would use las nubes when you refer to particular clouds, or clouds as a more specific set:

Mira las nubes; parecen montañas. – Look at the clouds; they look like mountains.
Las nubes tapan el sol. – The clouds are blocking the sun.

In this weather description, nubes without article is the natural, idiomatic form.

Why do we use the present tense está to talk about the current weather? Could we use another tense?

Spanish uses the present indicative to describe conditions that are true right now, including weather:

Hoy el cielo está cubierto de nubes. – Today the sky is covered with clouds.

Other tenses would change the time reference:

Ayer el cielo estuvo cubierto de nubes. – Yesterday the sky was covered with clouds.
Mañana el cielo estará cubierto de nubes. – Tomorrow the sky will be covered with clouds.

You wouldn’t use the present continuous (está estando cubierto) here; that’s not natural in Spanish. The simple present está is exactly what you want for “is (currently)” in weather descriptions.

How is cielo pronounced in Spain, and are there any pronunciation tips for this sentence?

In standard Peninsular Spanish (Spain):

cielo → [ˈθje.lo]
- c before i/e is pronounced like English th in think: θ
- cie sounds like thye in “th’yellow” (quickly together)
- Stress is on the first syllable: CIE-lo

Full sentence (Spain):
Hoy el cielo está cubierto de nubes.

Approximate guide:

Hoy → like English oy in boy, but a bit shorter.
el → like ell.
cielo → THYEH-lo.
está → es-TA (stress on the last syllable).
cubierto → cu-BYER-to (the b is soft; bie like bye but shorter).
de → like deh.
nubes → NUH-bes, stress on NU; b is soft.

Main Spain-specific point: cielo has a th sound at the start (θie-), not s.

Could I say Hoy el cielo está con nubes instead of cubierto de nubes?

You might hear con nubes in weather forecasts (e.g. cielos con nubes, intervalos nubosos), but:

Hoy el cielo está con nubes sounds odd or at least much less natural in everyday speech.
The more idiomatic options are:
- Hoy el cielo está nuboso.
- Hoy el cielo está nublado.
- Hoy el cielo está cubierto (de nubes).

Con nubes is more often used in set forecast phrases like:

Cielos despejados con algunas nubes. – Clear skies with some clouds.

In a simple descriptive sentence like yours, prefer está nublado, está cubierto, or está cubierto de nubes.

Is there any difference between Hoy el cielo está cubierto de nubes and Hoy el cielo se ve cubierto de nubes?

Both are correct, but they focus on slightly different things:

Hoy el cielo está cubierto de nubes.
States the objective condition: the sky is overcast.
Hoy el cielo se ve cubierto de nubes.
Literally: “Today the sky looks covered with clouds.”
Emphasizes appearance from your point of view.

In most weather-related contexts, people simply say está cubierto or está nublado.
Adding se ve adds a nuance of “it appears” or “it looks (to us) like this,” which you don’t really need unless you want to highlight perception.