Dear everyone

Are the following expressions natural?
1. It is getting dark.
2. It is growing dark.
3. It is becoming dark.
4. It is turning dark.

I suppose 1 and 2 are all right but I wonder whether 3 and 4 are natural.

I have only two examples of 'become dark', and as for 'turn dark' I have
none.

(a) A little over an hour passed.  It became dark in Phil's prison,
  but he had no means of lighting the gas.  There was a small bed in
  the room, and he made up his mind that he must sleep there.
                                   -- Horatio Alger, The Errand Boy
(b) Presently the sun set and it became dark, whereon the pair retired
  into the inner part of the cave and went to bed.
                                   -- Homer-Butler, The Odyssey

Thanks in advance.

SIRAISI Tomiio