I am not sure I understand the question, but perhaps this will answer it:

Definitions for it in my Webster's 3rd New International Dictionary include:

2a used as an expletive subject of an impersonal verb that expresses a simple condition or an action without implied reference to an agent about the weather ... or time.

It is raining or It is two o'clock are examples of 2a.

I am not sure I understand the question, but perhaps this will answer it:

Definitions for it in my Webster's 3rd New International Dictionary include:

2a used as an expletive subject of an impersonal verb that expresses a simple condition or an action without implied reference to an agent about the weather ... or time.

It is raining or It is two o'clock are examples of 2a.