If this isn't an endorsement for getting to a sunrise scene well before sunrise, I don't know what is (and the same applies for sticking around after sunset). This image was made 30 minutes before the sun was first visible in the gap between the far trees.
For color intensity comparison, here's the same scene 30 minutes later as the sun began to rise over the far shore. http://www.pbase.com/ed_k/image/102033293