Cada vez que veo un relámpago, cierro la ventana y apago la luz.

Cada vez que means every time that or simply whenever.

In this sentence, Cada vez que veo un relámpago means Every time I see lightning / a flash of lightning.

It introduces something that happens regularly or repeatedly:

• Cada vez que llueve, me quedo en casa. — Every time it rains, I stay home.
• Cada vez que lo veo, sonríe. — Whenever he sees him, he smiles.

Here veo is in the present indicative because the sentence describes a habitual, real action: this is something the speaker actually does whenever that situation happens.

• Cada vez que veo un relámpago... = Every time I see lightning...

You might see the subjunctive after time expressions when the action is in the future or not yet experienced:

• Cada vez que vea un relámpago, cerraré la ventana.
  Whenever I see lightning, I will close the window.

So:

• veo = real / habitual
• vea = future or hypothetical in this kind of structure

Yes. In English, lightning is usually an uncountable noun, but in Spanish relámpago is a countable noun meaning flash of lightning.

So:

• veo un relámpago = I see a flash of lightning
• In natural English, this is often just translated as I see lightning

Spanish can also use:

• veo relámpagos — I see lightning / flashes of lightning

But un relámpago is completely normal and natural.

These words are related but not the same:

• relámpago = flash of lightning (what you see)
• trueno = thunder (what you hear)
• rayo = often lightning bolt or ray; depending on context, it can overlap with relámpago

For a learner, a useful basic distinction is:

• veo un relámpago — I see lightning
• oigo un trueno — I hear thunder

Spanish often uses the present tense to talk about habitual actions, just like English does.

So this sentence means:

• Every time I see lightning, I close the window and turn off the light.

This is not about one specific moment; it is about a repeated habit or usual reaction.

The three present forms match that pattern:

• veo — I see
• cierro — I close
• apago — I turn off

Spanish often uses the definite article (el, la, los, las) where English might use the, a/an, or sometimes no article at all.

Here, la ventana and la luz refer to the specific window and light relevant in the situation — probably the one in the room the speaker is in.

So:

• cierro la ventana = I close the window
• apago la luz = I turn off the light

This sounds more natural in Spanish than una ventana or una luz, unless you specifically mean any one window or any one light.

Because Spanish usually omits subject pronouns when the verb ending already makes the subject clear.

• veo
• cierro
• apago

All of these clearly show I.

So Spanish normally says:

• Cada vez que veo un relámpago, cierro la ventana y apago la luz.

You could say yo veo, yo cierro, yo apago, but it would usually sound unnecessary unless you want emphasis or contrast:

• Yo cierro la ventana, pero él no.
  I close the window, but he doesn’t.

Apagar la luz means to turn off the light.

The verb apagar means to switch off, to extinguish, or to put out, depending on context:

• apagar la luz — turn off the light
• apagar el móvil — turn off the phone
• apagar el fuego — put out the fire

Its opposite is encender:

• encender la luz — turn on the light

The comma separates the introductory clause from the main action:

• Cada vez que veo un relámpago,
• cierro la ventana y apago la luz.

It helps show the structure clearly: first the condition/time idea, then the main actions.

In short:

• Cada vez que... = introductory dependent clause
• cierro... y apago... = main clause

In Spanish, this comma is very natural here.

Yes. The sentence has one subject understood throughout: I.

So Spanish naturally says:

• cierro la ventana y apago la luz

Both verbs share the same subject:

• (yo) cierro
• (yo) apago

This is exactly like English:

• I close the window and turn off the light.

There is no need to repeat the subject unless you want emphasis.

Sometimes yes, but cada vez que is more specifically every time or whenever.

Compare:

• Cuando veo un relámpago, cierro la ventana. — When I see lightning, I close the window.
• Cada vez que veo un relámpago, cierro la ventana. — Every time I see lightning, I close the window.

Both can be natural, but cada vez que emphasizes repetition more strongly.

Yes, it is perfectly natural in Spanish from Spain.

Everything in it is standard:

• Cada vez que for whenever / every time
• present tense for habitual actions
• relámpago for lightning flash
• cerrar la ventana
• apagar la luz

A speaker from Spain would understand and use this without any problem.