+1 to starting in the dark, regardless of the supposed nature of the emergency (at least in S. Arizona when I was active. I doubt seriously it has changed).

The sun was sinking into the west as I pulled out on the majority of operations. Standard gear was three sources of light, just like going into a cave.

We had many operations where it was clear that prompt reaction was crucial to lives and well-being, regardless of whether the sun was up or not.