You probably already have the Skull Hammer, right? Now all you need to do is go to Ice Ring Isle (it's somewhere down south-ish). When you're there, shoot a fire arrow in the dragon's mouth or somewhere around the dragon head. Then, just go in and get the Iron Boots. Then go back to Gale Isle, put on the Iron Boots, walk to the thing that's blowing the wind, and smash it with your Skull Hammer.