Iceland, the volcanic rock in the North Atlantic does not quite live up to its name when it comes to the weather in Iceland. Since a branch of the Gulf Stream flows along the south and west part of the island it greatly moderates the climate. However the stream brings the mild air in contact with the colder Arctic air which results in frequent weather canges and storms out of nowhere. It also couses more rain than the locals care for.
During summertime tourists should have that in mind. Bring rainwear, windbreakers, good walking shoes if you plan on hiking. Be sure to check with locals og the Icelandic Met office before taking to unknown territories. Remember, in the mountain areas Iceland weather can change from clear sunny weather to a snow blizzard in a blink of an eye.
Iceland Met Office : www.en.vedur.is