Nos quedamos adentro cuando llueve.

Nos is a reflexive pronoun that refers back to nosotros (we).

• quedarse = to stay / to remain (reflexive)
• nos quedamos = we stay (literally: we stay ourselves)

In this sentence, nos is necessary, because quedar without the reflexive pronoun usually does not mean “to stay (somewhere)” in the way English uses it.

Compare:

• Nos quedamos adentro. = We stay inside.
• Quedamos en ir al cine. = We agreed to go to the movies. (here quedar = to agree/arrange)

In Latin American Spanish:

quedar (non‑reflexive) commonly means:

• to be located: El hotel queda cerca. = The hotel is (located) nearby.
• to be left / remain (quantity): Queda poca comida. = There is little food left.
• to arrange/agree: Quedamos en vernos mañana. = We agreed to see each other tomorrow.

quedarse (reflexive) means:

• to stay / remain somewhere: Nos quedamos adentro. = We stay inside.
• to end up / be left in a state: Se quedó sin dinero. = He ended up without money.

So for “stay inside”, you want quedarse, not plain quedar.

It would sound odd or confusing in most contexts.

Without nos, quedamos is usually understood as:

• we end up / remain (in some result), or
• we agree/decide (as in quedamos en…).

To say we stay inside in the everyday sense (we don’t go out), you should use the reflexive:

• Nos quedamos adentro cuando llueve. ✅ (natural)

So for “stay (somewhere)”, learners should treat quedarse (with the pronoun) as the normal form.

Spanish often drops subject pronouns because the verb ending shows the subject.

• quedamos is 1st person plural (we).
• The reflexive pronoun nos also points to nosotros.

So Nos quedamos adentro already clearly means We stay inside.
You can say Nosotros nos quedamos adentro for emphasis (for example, contrasting with others):

• Ellos salen, pero nosotros nos quedamos adentro.
  They go out, but we stay inside.

All of these are possible, with slightly different flavors:

• adentro = inside (very common in Latin America in everyday speech)

  • Nos quedamos adentro cuando llueve.

• dentro = inside, often used as dentro de

  • noun
  • Nos quedamos dentro de la casa cuando llueve. = We stay inside the house when it rains.

• en casa = at home

  • Nos quedamos en casa cuando llueve. = We stay at home when it rains.
    This says at home, not necessarily just “inside” any building.

In much of Latin America, adentro and en casa are both very natural. Dentro (de) sounds a bit more formal or explicit, especially with a noun: dentro de la casa.

Yes, Nos quedamos dentro is grammatically correct and understandable.

Nuance/usage:

• In Latin America, adentro is more common than dentro when you mean simply “inside” with no noun after it.
• dentro de is very common before a specific place:
  
  • Nos quedamos dentro de la casa / del edificio.

So:

• Nos quedamos adentro. ✅ very natural in Latin America
• Nos quedamos dentro. ✅ correct, a bit less colloquial in some regions
• Nos quedamos dentro de la casa. ✅ very clear and natural

Cuando llueve uses the simple present and expresses a general/habitual situation:

• Nos quedamos adentro cuando llueve.
  We (generally) stay inside whenever it rains.

Cuando está lloviendo emphasizes the action in progress:

• Nos quedamos adentro cuando está lloviendo.
  We stay inside when it’s raining (while the rain is actively happening).

Both are possible, but:

• For a general habit or rule, cuando llueve (simple present) is more standard and natural.
• For talking about what you’re doing at this moment, you’d more likely say:
  
  • Nos quedamos adentro porque está lloviendo. = We’re staying inside because it’s raining (right now).

Weather verbs in Spanish usually appear without an explicit subject.
Llover (to rain) is used almost always in 3rd person singular:

• Llueve. = It’s raining.
• Nunca llueve. = It never rains.

Spanish doesn’t need a dummy subject like English it. The verb alone is enough.
So cuando llueve = when it rains.

Yes, but the meaning changes.

• cuando llueve (indicative) = whenever it rains / when it rains (general, habitual fact)
• cuando llueva (subjunctive) = when it rains (in the future / hypothetical, not yet realized)

In your sentence, we’re talking about a general habit, so:

• Nos quedamos adentro cuando llueve. ✅

Examples with llueva:

• Nos quedaremos adentro cuando llueva.
  We will stay inside when it rains. (talking about a future event)
• Voy a salir cuando deje de llover. / cuando pare de llover.
  I’m going to go out when it stops raining. (future/hypothetical stopping)

You can move it:

• Nos quedamos adentro cuando llueve.
• Cuando llueve, nos quedamos adentro.

Both are correct and natural. Starting with Cuando llueve just puts more emphasis on the condition when it rains. The comma after Cuando llueve is normally written in this order.

Present indicative of quedarse:

• yo me quedo = I stay
• tú te quedas = you stay (informal singular)
• él/ella/usted se queda = he/she/you (formal) stay
• nosotros/nosotras nos quedamos = we stay
• ustedes se quedan = you all stay (Latin America)
• ellos/ellas se quedan = they stay

Your sentence uses nosotros form:

• Nos quedamos adentro cuando llueve. = We stay inside when it rains.

You can keep the same structure and adjust for “today” and “because”:

• Hoy nos quedamos adentro porque está lloviendo.

Breakdown:

• Hoy = today
• nos quedamos = we are staying / we stay (present used for “are staying”)
• adentro = inside
• porque está lloviendo = because it is raining (right now / today)

Adentro by itself means simply inside (not outside), without specifying what:

• Nos quedamos adentro cuando llueve.
  We stay inside (in the building / in the house / indoors) when it rains.

If you want to be explicit about the place, you can add it:

• Nos quedamos adentro de la casa cuando llueve. = We stay inside the house when it rains.
• Nos quedamos adentro del edificio. = We stay inside the building.

So adentro alone = indoors / not outside; context usually tells you where.