اگر باران میآمد، کلاه و بارانی ام را با خودم میآوردم.

Because Persian usually does not use a dummy subject like English it in weather expressions.

English says it is raining and if it rained, but Persian can simply say:

باران می‌آید = it is raining / rain comes
باران می‌آمد = it was raining / if it rained

So leaving out a separate word for it is completely normal.

This is a common Persian way to talk about rain. Persian often uses آمدن (to come) with weather, so باران می‌آید / می‌آمد is a natural expression for it is raining / it was raining.

You could also hear:

باران می‌بارید = it was raining

That uses the verb باریدن (to rain / to fall, for rain, snow, etc.). Both are possible, but باران می‌آمد is very common and natural.

Both are imperfect forms made with می‌- plus a past stem.

• می‌آمد = was coming / would come
• می‌آوردم = I was bringing / I would bring

In Persian, this form can express:

• an ongoing past action,
• a habitual past action,
• or a hypothetical/conditional meaning.

So in a sentence like this, Persian uses these forms to express an unreal or hypothetical situation:

اگر باران می‌آمد، ... می‌آوردم
= If it rained / were raining, ... I would bring

Persian does not need a separate word exactly like English would here; the conditional meaning comes from the whole structure.

Because Persian handles many unreal or imagined conditions in a way that is somewhat similar to English.

Compare:

• English: If it rained, I would bring...
• Persian: اگر باران می‌آمد، ... می‌آوردم

Even though the verb forms look past-like, the meaning is not necessarily past in time. They can express something imagined, contrary-to-fact, or dependent on a condition.

A very common pattern is:

اگر + imperfect ..., imperfect ...

For example:

اگر وقت داشتم، می‌آمدم.
= If I had time, I would come.

So this sentence is following a very normal Persian conditional pattern.

Yes.

بارانی can mean different things depending on context:

• as an adjective: rainy
• as a noun: raincoat

In this sentence, it is clearly a noun because it appears with کلاه and is part of the object being brought:

کلاه و بارانی‌ام = my hat and raincoat

So here بارانی definitely means raincoat.

The ending -ام means my. In standard spelling, بارانی‌ام means my raincoat.

Persian often avoids repeating possessive markers with coordinated nouns when the meaning is already clear. So:

کلاه و بارانی‌ام
naturally means
my hat and raincoat

If you wanted to make both possessives fully explicit, you could say:

کلاه‌ام و بارانی‌ام

But that is more repetitive. The original version sounds natural and efficient.

را marks the direct object, especially when it is definite or specific.

Here, the whole phrase کلاه و بارانی‌ام is the thing being brought, so را comes after the whole coordinated object:

کلاه و بارانی‌ام را

That is normal Persian word order. You do not need a separate را after each noun.

So the structure is:

[direct object] + را + [verb]

In this sentence: کلاه و بارانی‌ام را ... می‌آوردم

با خودم literally means with myself, but idiomatically it means with me.

So:

با خودم می‌آوردم
= I would bring with me

It is not strictly necessary. You could say:

اگر باران می‌آمد، کلاه و بارانی‌ام را می‌آوردم.

That still means If it rained, I would bring my hat and raincoat.

Adding با خودم makes it closer to English bring ... with me and emphasizes that the speaker would personally have those items along.

Because Persian, like English, often distinguishes between bring and take based on the point of reference.

• آوردن = to bring (toward the speaker or the relevant destination)
• بردن = to take (away from the speaker or reference point)

So می‌آوردم means I would bring. In this sentence, the speaker is imagining coming somewhere and having the hat and raincoat with them, so bring is the natural choice.

If the perspective were different, می‌بردم might be used instead.

A more standard spelling is:

اگر باران می‌آمد، کلاه و بارانی‌ام را با خودم می‌آوردم.

The version you saw is understandable, but it leaves out the usual half-spaces in places like:

• می‌آمد
• بارانی‌ام
• می‌آوردم

A rough pronunciation is:

agar bârân mi-âmad, kolâh o bârâni-am râ bâ khodam mi-âvardam

A couple of useful notes:

• The written و meaning and is often pronounced o in natural speech.
• می‌- is attached to the verb with a half-space in standard writing.
• Casual typing often ignores these spacing rules, so learners will see both styles.