Toby it will be very hot and humid, especially near Darwin. I find even fit people can struggle in the heat and humidity here if not accustomed to it and we are further south. Can be correct about the water holes but I think Darwin has already been getting some rain so I would check that out. I have also found that when they hang around the water the bulls mix in with more other animals than usual and it can be hard to stalk in close as opposed to finding a lone bull. We do get the bulk of our rain later on but its a big call to say it will probably not be that wet. I think there will be enough rain around Darwin before then to negate the available water holes theory. If you hunt in December you will earn it.