Ad agosto bevo più acqua perché fa molto caldo.

Ad is just a used before a word that starts with a vowel, in this case agosto.

So:

• a + agosto → ad agosto

This helps the phrase sound smoother. In modern Italian, adding d is not always required before every vowel, but ad agosto is very common and natural.

Yes. In agosto is also correct.

Both can mean in August, but they can feel slightly different depending on context and style:

• ad agosto = at/in August, often when talking about a general time point or period
• in agosto = in August, also very common

In everyday Italian, both are acceptable here.

Italian often drops subject pronouns when they are not needed.

Bevo already means I drink, because the verb ending -o shows the subject is I.

So:

• bevo = I drink
• io bevo = I drink too, but with extra emphasis on I

You would usually add io only if you want contrast or emphasis, for example:

• Io bevo più acqua, lui meno.
  I drink more water, he drinks less.

Bevo is the first person singular present tense of bere (to drink).

Conjugation of bere in the present:

• io bevo = I drink
• tu bevi = you drink
• lui/lei beve = he/she drinks
• noi beviamo = we drink
• voi bevete = you all drink
• loro bevono = they drink

So in the sentence, bevo tells you the speaker is talking about themself.

Because acqua here is an uncountable noun used in a general sense.

In Italian, when you talk about more + uncountable noun in a broad way, you usually do not use an article:

• più acqua = more water
• più caffè = more coffee
• più tempo = more time

Più dell’acqua would mean something different, like more than the water or would need a specific comparison.

If you want to make the comparison explicit, you can say:

• bevo più acqua del solito = I drink more water than usual
• bevo più acqua di prima = I drink more water than before

Here, più means more.

It is making a comparison, even if the second part is not stated explicitly. The idea is:

• bevo più acqua = I drink more water

Usually, the comparison is understood from context, such as:

• more than usual
• more than in other months
• more than before

So più here is a comparative word, not most.

Because the word is stressed on the last syllable, and in Italian a final stressed e is written with an accent:

• perché

The accent is not optional here.

Also, perché can mean both:

• because
• why

The meaning depends on how it is used in the sentence:

• Bevo più acqua perché fa caldo. = because
• Perché bevi più acqua? = why

For weather and general environmental conditions, Italian usually uses fare:

• fa caldo = it’s hot
• fa freddo = it’s cold
• fa bel tempo = the weather is nice

This is a standard Italian pattern.

By contrast, è caldo usually describes a person, object, or place as being warm/hot:

• Il caffè è caldo. = The coffee is hot.
• La stanza è calda. = The room is warm.

So in this sentence, fa molto caldo is the natural way to talk about hot weather.

It is an impersonal expression.

In English, you say it is hot, where it does not refer to a real thing. Italian often does something similar but without saying a subject pronoun:

• fa caldo = it’s hot

So fa is third person singular, but there is no real, named subject.

In fa caldo, caldo is part of a fixed expression and behaves more like a noun meaning heat, not like a normal adjective agreeing with another noun.

That is why you say:

• fa caldo
• fa freddo

not:

• fa calda
• fa fredda

But when caldo is used as a normal adjective, it does agree:

• L’acqua è calda. = The water is warm.
• Il tè è caldo. = The tea is hot.

So in your sentence, caldo stays in the standard form used in the weather expression.

Yes. Italian word order is fairly flexible.

The original sentence:

• Ad agosto bevo più acqua perché fa molto caldo.

puts the time expression first, which sets the scene: In August...

You could also say:

• Bevo più acqua ad agosto perché fa molto caldo.

This is also correct. The difference is mostly one of focus and style, not basic meaning.

Putting Ad agosto first sounds very natural when you want to frame the whole statement around that time period.

In Italian, names of months are normally written with a lowercase letter:

• gennaio
• febbraio
• marzo
• agosto

This is different from English, where months are capitalized.

So ad agosto is correct, not ad Agosto, unless there is some special stylistic reason.