Yo Ho bznuts,
I am a bit of a botanist so to speak. I love horticulture, and growing exotics is one of my bags. I have both a small hothouse and a fair greenhouse. In all my years of learning and growing, I was taught that you really shouldn't water at night as that might set you up for root problems, basically they say water during early am hours. Watering lawns is a good example, you do it at an optimal time in the morning. But also remember that it rains whenever.
I guess I would advise early am if your grow is outdoors, and at the beginning of your light cycle if you are doing indoors. Just my $0.02
smoke in peace
KingKahuuna