if bud is anything like your lawn its best to water about 3 hours before the sun comes up
Thats because when you water your lawn you soak the grass leaves and everything. If you water at sunset your grass stays wet all night increasing the chance of a variety of fungus diseases. Watering your lawn in the evening does not mean you are going to definitely have problems, It's just bettering your odds of no problems if you can water early in the day where the foliage can dry off well.
Most people don't soak the canopy of their weed plants where it could even be a factor, as far as foliage being wet. So in my opinion you could water about any time of day, but I water in the AM generally, because by the time I water they are really very dry, and they suck up some good moisture and nutes all day under the lights, and go into the cool dark period with the soil at least a little better drained and dried out.