https://siteanalytics.compete.com/news.ycombinator.com
I have not found much in HN submission history and I am not sure how to read this data:
* is compete.com data reliable?
* could this be artificial? (e.g. DDoS)
* is this related to a particular event?
* does 1M unique visitors makes sense?
This also may be relevant: http://www.google.com/trends/explore#q=hacker%20news