Pluvia cives non impedit quominus ad templum veniant.

The sentence breaks down like this:

• Pluvia = rain; nominative singular, the subject
• cives = the citizens; accusative plural here, the direct object
• non impedit = does not prevent
• quominus = introduces a clause after a verb of hindering/preventing; here it means something like from or that ... should not
• ad templum = to the temple
• veniant = they may come / they come; present subjunctive, referring to cives

So structurally it is:

Rain does not prevent the citizens from coming to the temple.

Because pluvia is in the nominative singular, and the verb impedit is also third-person singular: it prevents.

That match tells you that pluvia is the thing doing the preventing.

So:

• pluvia impedit = the rain prevents
• not the citizens prevent

The form cives can be either nominative plural or accusative plural, so by itself it is ambiguous.

But the rest of the sentence makes its role clear:

• pluvia already fits the subject position
• impedit is singular, so it cannot go with plural cives as its subject
• therefore cives must be the direct object

So the sentence means:

• the rain does not prevent the citizens...

not

• the citizens do not prevent the rain...

After verbs of hindering or preventing, quominus introduces the action that is being prevented.

In this sentence, quominus ad templum veniant means:

• from coming to the temple
• or more literally, that they should come to the temple no less

You do not need to force the literal etymology when translating. In normal English, after impedire, quominus is best understood as:

• from
• or that ... not

So:

• cives non impedit quominus ad templum veniant
• = it does not prevent the citizens from coming to the temple

Because quominus clauses after verbs of hindering/preventing normally take the subjunctive.

So this is a standard construction:

• impedio quominus + subjunctive
• prevent from doing something

That is why Latin uses:

• veniant
  not
• veniunt

The subjunctive here is not mainly about uncertainty in the English sense. It is there because the grammar of the construction requires it.

Because the main verb is in a primary tense:

• impedit = present tense

With a present-tense main verb, Latin normally uses the present subjunctive in a subordinate clause when the action is simultaneous or subsequent.

So:

• impedit ... veniant = present main verb + present subjunctive

If the main verb were in a past tense, you would expect the imperfect subjunctive instead:

• impediebat quominus ad templum venirent
  = was preventing them from coming to the temple

No, not in the sense of canceling out or producing a positive.

The non negates the main verb:

• non impedit = does not prevent

The word quominus belongs to the subordinate clause construction used after verbs of hindering.

So the idea is:

• The rain does not prevent the citizens from coming to the temple

not

• The rain prevents the citizens from not coming

A learner may feel that there are two negatives, but this is just how Latin expresses this kind of idea. You should read non impedit quominus as a normal idiom with verbs of prevention.

Because ad with the accusative often means to or toward a place.

So:

• ad templum = to the temple

This is a straightforward way to express motion toward a destination.

A learner may wonder about in templum. That can mean into the temple, with a stronger sense of entering the inside. But ad templum simply means going to the temple, which fits the English translation well.

Because its subject is cives, which is plural.

Even though cives is not the subject of the main verb impedit, it is the understood subject of the subordinate verb veniant.

So:

• cives ... veniant = the citizens ... come

If there were only one citizen, you would expect singular veniat.

In this kind of sentence, Classical Latin commonly uses a subordinate clause with quominus plus the subjunctive after a verb like impedio.

So impedit quominus veniant is a very natural construction.

English says prevent someone from coming, with from + -ing, but Latin does not usually mirror that structure directly here. Instead it prefers the finite clause:

• impedire quominus veniant

So a learner should recognize this as a standard Latin pattern rather than try to force an English-style infinitive construction onto it.

It is perfectly normal Latin word order.

Latin word order is much freer than English word order, because endings show grammatical function. This sentence puts the words in a clear and natural sequence:

• Pluvia — the subject first
• cives — the object next
• non impedit — the main verb
• quominus ad templum veniant — the subordinate clause

English relies heavily on word order, but Latin relies more on case endings and verb forms. So even if the order changed, the meaning would usually remain the same.

For example, Latin could rearrange the sentence for emphasis, but the grammar would still show:

• pluvia = subject
• cives = object
• veniant = subordinate verb referring to cives

A fairly literal unpacking would be:

• The rain does not hinder the citizens, with the result that they may come to the temple

But that is not natural English. The best smooth translation is:

• The rain does not prevent the citizens from coming to the temple

That is usually the best way to understand the Latin idiomatically.