Blog numbers

This puzzles me.  For days they remain "average" and then suddenly, for no good reason, the numbers nearly double.  Perhaps the blog gets mentioned somewhere and this attracts new visitors? The post content always varies, so I very much doubt it is this. There have been few external links in my recent posts, so I don't think it is people leaving and returning and being double counted.  My amateur radio blog attracts about 10 times more visitors than this blog.