But being cloudy and raining affects how soon it gets dark.
The one man who testified he and his wife heard a struggle and he told he not to go out but hearing a gunshot he did--I got impression from his testimony it was dark, though I can't say why.
Jon Goodman could see T atop Z so it couldn't have been that dark, unless he used a flashlight.
@Cigar, I remember reading somewhere about weather and darkness and such way early on in the case, it's out there somewhere, but i can't find it.