goodroi - 6:49 pm on May 13, 2013 (gmt 0)
I am not sure if it is a time triggered boost or if its just that during the high season more bloggers/news site are talking about you and linking more but I have seen the same thing to my own sites.
ps People should not forget to take into account that Google personalizes rankings. One of my clients searched for her site everyday leading up to the holiday season and this led to Google personalizing her rankings to show her site on page 1. One day she accidentally cleared her cookies and she thought Google had banned her site because she then saw the real rankings where her site wasn't on the first page.