I've been noticing an increase in this phenomenon lately and it is making me very nervous. The spike is about 20 to 25% of the previous hour and clicks go back to normal right after midnight.
I've noticed a spike at about midnight *UK* time, but hadn't noticed one midnight Google time.
However, the latter would make sense if G was trying to flush stats into the central database to credit clicks and impressions for the correct Google day.
Rgds
Damon
These are actual visitors and page impressions - not the Adsense stats page.
Well, I often get a visitor spike (from the US) around midnight UK time, and remember that there is a well known peak at about 7pm UK time (home from school/work) coinciding with US lunchtime, so maybe your visitors have some similar synchronicity?
Rgds
Damon
