Learn Hardcore Spanish (Latin America): Lo raro es lo silencioso que está el bosque antes de la tormenta. - The strange thing is how quiet the forest is before the storm.

Here lo is the neuter definite article, not the direct‑object pronoun. It turns an adjective into an abstract noun: lo raro ≈ “the strange thing/what’s strange.” The neuter lo is invariable (it doesn’t show gender or number) and is used to talk about ideas/qualities in general, not specific people or objects.

Why is lo used twice in the sentence?

Each lo does a different job:

Lo raro = “the strange thing” (nominalizes the adjective).
lo silencioso que… = a set phrase that means “how quiet … is” (expresses degree).

You need both to keep the original structure: “What’s strange is how quiet the forest is…”

How does the pattern lo + adjective + que work?

It expresses degree and is often translated as “how + adjective.” After que, you get a clause.

No imaginas lo caro que es vivir aquí. = “You can’t imagine how expensive it is to live here.”
¡Lo silencioso que está el bosque! = “How quiet the forest is!”

In your sentence, lo silencioso que está el bosque is a noun‑like clause meaning “how quiet the forest is.”

Could I say qué tan or cuán instead of lo … que?

qué tan + adj is very common in many parts of Latin America, but mainly in direct questions/exclamations: ¿Qué tan silencioso está el bosque? As an embedded clause after a verb like “es,” Spanish typically prefers lo + adj + que. So, Lo raro es qué tan silencioso… sounds odd to many ears.
cuán + adj is correct and fairly formal/literary: Lo raro es cuán silencioso está el bosque… It’s acceptable, but in everyday Latin American Spanish, lo … que is the most neutral choice for embedding.

Why is it está and not es with silencioso?

estar + adj describes a temporary/state condition: El bosque está silencioso = the forest is (right now) quiet.
ser + adj describes an inherent/defining trait: El bosque es silencioso = the forest is generally a quiet place.

Because the clause mentions a specific timeframe—“before the storm”—the temporary state with estar is natural.

Can I rewrite it as Lo raro es que el bosque esté tan silencioso antes de la tormenta?

Yes. That’s very natural. With evaluative expressions like (lo) raro es que…, Spanish normally uses the subjunctive (esté) in the following clause.

Nuance:

Lo raro es lo silencioso que está… highlights the degree (“how very quiet it is”).
Lo raro es que el bosque esté tan silencioso… states the odd fact that it’s quiet (you can add tan to express degree, but it doesn’t carry the same open‑ended “how” nuance as lo … que).

Why doesn’t que have an accent in lo silencioso que está?

Because it’s not the interrogative/exclamative qué. In the construction lo + adj + que, que is a conjunction and is written without an accent. Compare:

¡Qué silencioso está el bosque! (direct exclamation; accented)
Lo silencioso que está el bosque (embedded structure; no accent)

Why is it antes de la tormenta and not just antes la tormenta?

With a noun, Spanish uses the preposition de: antes de + noun. Hence, antes de la tormenta. If you follow with a verb, use antes de que + subjunctive:

antes de que empiece la tormenta = “before the storm starts.”

Is the word order que está el bosque normal? Could I say que el bosque está?

After lo + adj + que, Spanish very often uses verb–subject order: que está el bosque. You might hear que el bosque está, but it’s less idiomatic here. Stick with que está el bosque as the natural pattern.

Does silencioso agree with lo or with bosque?

With bosque. In lo + adj + que + clause, the adjective inside the clause agrees with the subject of that clause:

No imaginas lo cansadas que están las niñas. (fem. plural to match las niñas) Here, silencioso is masc. singular to match el bosque. The initial lo is invariable and doesn’t control agreement.

Could I use a noun instead and say: Lo raro es el silencio del bosque antes de la tormenta?

Yes. That’s correct and natural. It simply shifts the focus:

el silencio del bosque states the presence of silence.
lo silencioso que está el bosque emphasizes the degree (“how quiet it is”).

Are there synonyms for raro? Do they change the tone?

extraño: very close to “strange,” slightly more neutral/formal.
curioso: “odd/interesting” rather than flatly “weird.”
insólito: “unusual/unheard of,” stronger and more formal. All fit: Lo extraño/curioso/insólito es lo silencioso que está el bosque…, with subtle tone differences.

Why not use the adverb silenciosamente?

Spanish uses adjectives with estar to describe states/conditions of the subject: está silencioso. The adverb silenciosamente modifies actions (“He walks silently” = camina silenciosamente), not states with estar.

How do you pronounce raro here?

Word‑initial r in raro is a trill [rr]. The second r (between vowels) is a single tap. So you trill the first “r” and tap the second.
In most of Latin America, ci/cio in silencioso sound like an “s” (see‑len‑SYO‑so).
Liaison is normal: que está often flows as “queestá” in speech.

What’s the overall grammar structure of the sentence?

It’s a pseudo‑cleft style with a copula:

Subject (nominalized quality): Lo raro
Copula: es
Predicate complement (embedded exclamative of degree): lo silencioso que está el bosque
Time adjunct: antes de la tormenta

So it literally organizes as “The strange thing is [how quiet the forest is] [before the storm].”