बाहर बारिश हो रही है, इसलिए मैं आपकी आवाज़ नहीं सुन सकता।

It is raining outside, so I cannot hear your voice.

Breakdown of बाहर बारिश हो रही है, इसलिए मैं आपकी आवाज़ नहीं सुन सकता।

• मैं: I
• होना: to be
• आपका: your
• नहीं: not

Questions & Answers about बाहर बारिश हो रही है, इसलिए मैं आपकी आवाज़ नहीं सुन सकता।

Why is there no word for it, as in English it is raining?

Hindi does not need a dummy subject like English it in weather expressions.

So English it is raining becomes simply:

बारिश हो रही है
literally, rain is happening

That is completely normal Hindi. There is no need to add a word meaning it.

What does बाहर mean here, and why is it placed at the beginning?

बाहर means outside or outdoors.

At the beginning of the sentence, it sets the scene:

बाहर बारिश हो रही है = It’s raining outside

Hindi often puts time/place words early in the sentence, though word order can be somewhat flexible. Here, starting with बाहर sounds very natural.

Why does Hindi say बारिश हो रही है instead of just using a simple verb meaning rains?

Hindi commonly expresses weather events like this with होना plus the progressive form:

बारिश हो रही है
literally: rain is happening

This is the usual way to say it is raining.

So:

• बारिश = rain
• हो रही है = is happening / is going on

Even though it sounds different from English, this is one of the standard Hindi patterns for weather.