Although you are going in the Southern Summer , Tierra Del Fuego and the adjacent Antarctic area are blighted by strong winds which can carry a high chill factor and frequently hail. Thermal t shirts and layers with a good waterproof and windproof jacket on top are essential. A warm hat to cover the ears and woolen gloves and thick socks and "sensible shoes". You may not need it all but you just might. If it rains it will be driven into every seam in your jacket therefore if you get wet try to stay out of the wind. Hope the weather is favourable for you.