For any long-distance hike in Iceland, layers are the way to go. While the trails through the interior of the island are only open in the summer months, weather in Iceland is changeable and packing a waterproof jacket and wearing sturdy, waterproof hiking boots is essential. You’ll want a pair of comfortable trousers that dry quickly (not jeans!) in case of sudden rain and a warm jumper or fleece and a sports t-shirt to account for cold days and warm weather.