I've only seen the word 'grauenkalt' in a line from the song, 'Dieses Leben,' by Juli.
The line is:
"Diese Nacht ist grauenkalt und schwer."
I looked up the verb 'grauen,' and it means both 'to dawn' (as in, 'a new day is dawning,' which doesn't really make sense in this context) and 'to dread,' which makes a little more sense and could mean 'the night is dreadfully cold,' which is what I'm assuming it means.
What I'm wondering is, is this a real word or something that was made up for the song? At first I thought it was a typo and someone forgot to hit the space bar between 'grauen' (meaning gray) and 'kalt,' but that would be 'grauekalt' (with no 'n' in the middle). And that would mean that the night is gray, which also makes no sense.