Hummingbirds stay here all winter long and to feed them, the sugar water must be warm. The feeders must have some form of heat, such as a night light bulb. If not, the birds will try to feed as early as 4 a.m. and because the water will be very cold, they could freeze and die.
Their metabolism slows down at night by going into torpor, similar to hibernation. When they wake up they need the warmth of sugar water as they expend a great deal of energy flying. The Backyard Bird Shop has all the information about hummingbirds and you can build a lighted feeder; just look at “Do It Yourself” online.