En juillet et en août, je ferme les volets l’après-midi pour garder la maison fraîche.

French normally uses en with months:

• en juillet
• en août
• en décembre

So this is the standard way to say in July and in August. You would not say au juillet.

Repeating the preposition is very natural in French:

en juillet et en août

It makes the sentence sound balanced and clear. You may sometimes hear en juillet et août, especially in faster speech, but repeating en is the safer and more standard choice.

Here the present tense expresses a habit or routine.

So je ferme les volets means something like:

• I close the shutters
• I close the shutters regularly
• I close the shutters in summer afternoons

French uses the simple present for habitual actions just like English often does.

Les volets are shutters, usually the shutters on the outside of a house or window.

This is different from:

• les rideaux = curtains
• les stores = blinds

So the sentence is specifically about closing shutters to keep the heat out.

French often uses the definite article le / la / les where English would use a possessive like my or the, especially when the ownership is obvious from context.

So:

• je ferme les volets = I close the shutters

Because we already understand they are the shutters of my house. If you said mes volets, that would sound more emphatic or contrastive, as if you were stressing that they are my shutters.

L’après-midi can function as a time expression meaning in the afternoon or, in a habitual context, in the afternoons.

So:

• je ferme les volets l’après-midi = I close the shutters in the afternoon / in the afternoons

French often uses this kind of bare time phrase without an extra preposition.

A related form is dans l’après-midi, but that often means sometime during the afternoon, while l’après-midi is very natural for a general routine.

In standard modern French, après-midi is usually treated as masculine:

• un après-midi

Some speakers and regions also use the feminine, but masculine is the safest choice for learners.

In this sentence, you cannot see the gender because le or la becomes l’ before a vowel:

• l’après-midi

Pour + infinitive expresses purpose. It means to or in order to.

So:

• pour garder la maison fraîche = to keep the house cool

This structure is very common in French when you want to explain why someone does something.

Here the idea is:

• I close the shutters in order to keep the house cool.

Yes, that is also possible:

• Je ferme les volets pour que la maison reste fraîche.

This means almost the same thing.

The difference is grammatical:

• pour garder... = pour + infinitive
• pour que... reste... = pour que + subjunctive

The original sentence is simpler and very natural.

Because fraîche agrees with la maison, which is feminine singular.

• masculine singular: frais
• feminine singular: fraîche

So:

• un appartement frais
• une maison fraîche

This adjective is a little irregular, so it does not become feminine by just adding -e.

In French, many adjectives come after the noun, and frais / fraîche is normally one of them when it describes temperature or physical freshness.

So:

• la maison fraîche = the cool house

This is the usual word order. English often puts adjectives before the noun, but French does not always do that.

Yes. French is fairly flexible with time expressions.

The original sentence:

En juillet et en août, je ferme les volets l’après-midi...

puts the seasonal setting first. That sounds very natural.

You could also say things like:

• L’après-midi, en juillet et en août, je ferme les volets...
• Je ferme les volets l’après-midi, en juillet et en août...

These are possible, but the original version is smooth and clear.