Look at some of todays surprising top keywords:
8: 1726 cards
10: 1551 car
18: 1052 video
19: 1043 movie
These are pretty high keywords on any list, but they are exceptionally high today. Why? It's the 'ride the wave' thing again. Holiday - fathers day here in the US.
If you tune into the holidays on your sites with a specific holiday 'live forever' page, you can ride some of these traffic peaks year-after-year. I have Xmas pages from four years ago that make that once-a-year resurection to high traffic. Since they are such old pages, search engines loved them this last xmas.
The same is true for the other holidays, monthly topics, and seasonal activity.
When is the next big 'stoked search engine day'? Well ok, it's not actually a day, but rather an entire week of mega traffic. It's not to far away. When is it, and why?