What does this mean? "And, again, he saw himself in a green parl talking to an old man, a very old man, and the wind from the park was cold...

This line comes from the part after the old lady burned
herself up, where Montag is starting to feel that something is wrong with his society. 
He is looking at the lists of banned books and starts thinking of the park and the cool
wind.

To me, what is going on here is that Montag is
starting to feel unhappy with the society.  I think that you need to focus on two
things.  First, you should think about how there is an emphasis on cool in this
passage.  I think this is supposed to contrast with fire and the heat of the current
society.  So the cool symbolizes that Montag is thinking of a different kind of
society.  Second, you should think about who the old man is.  I think it is Faber.  I
think that this is foreshadowing how Montag will use Faber as a resource for his
rebellion against the society.