The climate is mild in Iceland, 0°C on average in winter and +13°C in summer. It rains a lot in Iceland and it can be windy. So, what kind of clothing to take with you? Here is my advice for a winter trip:
1 Woolen underwear, longjohns and long-sleeved shirt. Woolen socks.
2 Fleece sweater or warm sweater.
3 Parka or a warm wind-proof jacket.
4 Hats and gloves.
5 Hiking boots or winter boots.
6 Full rain-gear.
In summer you don’t need the woolen underwear but you need a warm sweater or a jacket, possibly a parka (early and late in summer), hiking boots and definitely a rain-gear.