The average temperature in iceland is around 15° Celsius. I am not sure how much that is in Farenheit but it is pretty cool for most europeans. In germany we get up to 40 or 50° Celsius in the summer but it is around 25° the most time.
Although the averga temperature is only 15°C we had up to 25° last week and some people i talked to said that this was also the case in the last four weeks.
Nice weather, blue sky and no rain, wonderful nature... wow. If it wasn't this expensive i would fly over to iceland again this fall. =)
The great thing is that you will find nearly no bugs on iceland. You can sleep everywhere without to watch out for snakes or bugs or anything that you just do not like in your tent. xD