As another posted, go the solar way, but that's initially expensive.
With extension cords, if you're like me and have to use more than one to get to the water/coop:
At the point where you plug two cords together, wrap with some duct tape (doesn't need but one or two wraps, just enough to hold them together), then cut a 'V' notch in the end of a 2x4 that is about 10" long. Stand the 2x4 up on end with the 'V' on top, place the cord in the 'V' so that the 'connection' is off the ground. Put a 5 gallon bucket over the 2x4 and cords and place a concrete block (or big rock or anything heavy) on top of the bucket to keep it from blowing over. This way when it rains or snows, you don't have to worry about the 'connection' between two cords getting wet and popping a circuit breaker.