I've made three summer visits to Iceland, all in August-September.  Nearly all the photographs included here were made on a trip to the West Fjords, and  a subsequent circumnavigation .  A quick glance at the photographs here will tell you that the big difference between summer and winter is simply that in summer there's not usually snow at road level .  It certainly isn't a time of wall to wall blue skies and T shirts;  though to be fair I have had T shirt days in Iceland- just not many. 

But the real difference is that you can get around.  You can drive yourself, and negotiate the mass of gravel roads as well as the tarmac, and this brings a lot more areas into play. With that and the longer days one gets a lot more photographs, and you don't have to sacrifice the action in the skies either.  All told, for me it's one of the very best summer locations, and even with the inevitable rain we came back with a lot of pleasing photographs.