Our first attempt in foul weather was thwarted and we stopped at p-horn. We finally had bright sunny clear weather and Kiefer and I made a late day dash up to the top! The last few kilometers to/from the actual summit were interesting, over volcanic rock, muck and moss. Made it back to p-horn just as the sun was going down. Incredible views of Reykjavik and the Atlantic ocean from there! Popular night hike for locals! Hiked out by headlamp.