Al novembre, de vegades sentim el tro abans de veure un llampec.

In Catalan, names of months are normally written in lowercase: gener, febrer, març, abril, novembre, etc.

That is different from English, where November is capitalized. In Catalan, you only capitalize it if normal capitalization rules require it, such as at the beginning of a sentence.

Al novembre means in November or during November.

Here, al is the contraction of a + el. Catalan often uses this kind of structure in time expressions. So:

• a + el = al
• al novembre = in November

This is a very natural way to place the action in that month.

The comma separates the introductory time phrase from the rest of the sentence.

So the sentence is structured like this:

• Al novembre = time setting
• de vegades sentim el tro abans de veure un llampec = main statement

In short sentences, punctuation can sometimes vary, but this comma is very normal and helps readability.

De vegades means sometimes or at times.

The singular noun vegada means time in the sense of occasion. So de vegades is an adverbial expression meaning something happens on some occasions.

You can think of it as functioning like one adverb:

• De vegades plou. = Sometimes it rains.
• De vegades sentim el tro... = Sometimes we hear thunder...

Catalan usually leaves out subject pronouns when they are not needed. This is called a pro-drop language.

The verb form sentim already tells you the subject is we:

• sento = I hear
• sents = you hear
• sent = he/she hears
• sentim = we hear

So nosaltres is unnecessary unless you want emphasis or contrast.

Because sentir usually means to hear, while escoltar means to listen.

That is similar to the English difference between:

• hear = perception happens
• listen = you do it intentionally

With thunder, the natural idea is that you hear it, not that you deliberately listen to it. So:

• sentir el tro = hear thunder
• escoltar música = listen to music

Also, sentir can sometimes mean to feel, so context matters. Here it clearly means to hear.

This is about how the speaker is presenting each thing.

• el tro = the thunder, or more naturally in English just thunder
• un llampec = a lightning flash / a flash of lightning

In this sentence, el tro refers to thunder as the phenomenon being heard, while un llampec refers to one specific flash.

So the contrast is:

• el tro = thunder in a general sense
• un llampec = one flash

If you changed the meaning slightly, you could also say un tro to mean a clap/peal of thunder.

Because in Catalan, when before is followed by an infinitive, you normally use abans de + infinitive.

So:

• abans de veure = before seeing
• literally, before to see

This is very common in Catalan grammar.

Because after abans de, Catalan uses the infinitive when the subject is the same as in the main clause.

Here the subject of both actions is we:

• sentim = we hear
• veure = see

So the full idea is:

• we hear thunder before seeing lightning

Catalan does not need to repeat we with a second conjugated verb here.

If you wanted a full clause with its own verb, Catalan would normally use a different structure, usually abans que plus subjunctive.

Because veure means to see, while mirar means to look at.

That is close to the English difference between:

• see = perceive with your eyes
• look at = direct your eyes toward something intentionally

A lightning flash is something you suddenly see. The sentence is not emphasizing the act of deliberately looking, so veure is the correct choice.

Yes, Catalan word order is fairly flexible, especially with time expressions like Al novembre and adverbs like de vegades.

For example, these are possible:

• Al novembre, de vegades sentim el tro abans de veure un llampec.
• De vegades, al novembre, sentim el tro abans de veure un llampec.

The original version is natural because it first sets the time frame, then gives the frequency.

Yes. Both are masculine:

• el tro
• un llampec

That is why the articles are el and un, not la or una.

This is something English speakers often have to memorize, since English nouns usually do not have grammatical gender.