August has not been kind to President Obama the last five years. For that matter, neither have the rest of the summer months.

Newly released Gallup polling data show Obama's job approval rating has tended to decline from June to August during the five years he has been in the White House. August has been the president's worst month overall -- he has averaged under a 46 percent job approval rating.

As Gallup notes, Obama's averages during the early months of the year have been boosted by his sky-high numbers when he first entered office, as well as the surge he experienced in May 2011 after the killing of Osama bin Laden. But the decline during the summer months can't be explained by any single events. In other words, its been a pretty steady drop-off each year.

It's not surprising. August is when Congress leaves town for a month-long recess and when the president typically vacations. Stories about what didn't get accomplished before the recess tend to pile up, and unrest and dissatisfaction at town halls around the country (especially in 2009, amid the heated health-care debate) tend to get more attention.

Obama isn't the only president to experience a summer slowdown. In fact, the last two presidents went through something similar -- albeit not as steep and sustained -- as the following charts show.

Going all the way back to 1945, the summer months have tended to be low points for U.S. presidents -- but no lower than September and October.