A moist environment with light winds creates optimal conditions for a mature deer to use his sniffer and sneak around without making much ruckus.......for me light drizzle is a go.
Just after a heavy rain, deer stand up shake off and start milling around no matter the time of day....another green light, I like to watch for those heavy storms and time it so I get to my stand or blind as the rain is slowing down and starting to stop.