An ELT Glossary : Empty "it" / Dummy Subject

Empty "it" (also known as the dummy subject) is a pronoun that has no referent and no meaning, but which is syntactically necessary in order to produce a grammatical sentence. Some examples :

It's raining
It's hot.
It's time to go.
It's already lunchtime.
It's late.
It's a long way to Tipperary.
It wasn't very nice in the hotel.

It makes no sense to ask What is raining? What is late? What's a long way to Tipperary? etc. These are verbs which have no real subject - but syntactically  English demands that one is present. To "fill the gap" the dummy pronoun it is used.

For a list of the uses of  the dummy pronoun it,  see