Heartsizedfarm- yes it is big enough for a weasel. It is 2x4 welded wire, so yes it is big enough for a weasel. I don't think we have them here though. Our main preds are possum, coon, coyotes and hawks. My main run does not have a cover but I only keep adult chickens in it. Knock on wood I have not had a problem with hawks.
Don't just knock on wood. Lay down some wood! Ha! Give them some brush or branches or hiding places in your run. They scurry to safety trying to get under something if they see an aerial predator, so give them that "bunker". Could save a life.