Obama had higher approvals in the earlier months in the years of his presidency because of events such as the death of al-Qaida founder Osama bin Laden, Gallup said.
There wasn't one reading in any June, July or August during the last five years that significantly lowered the average approval rating for Obama in those months, the Princeton, N.J., polling agency said. Rather, the summer ratings exhibited a consistent decline.
Gallup said its review indicated Obama's job approval rating hasn't increased from the prior month in any of the Junes, Julys or Augusts during his presidency, showed a decline in 13 of those 15 months, and no change in the other two.
Gallup said the historical information could explain the decline in Obama's approval rating from 49 percent in May to 45 percent in August.
Obama's immediate predecessors, George W. Bush and Bill Clinton, did not have the same month-to-month drop in approval rating in summer as Obama, but both Bush and Clinton's lowest approval averages by month were in June, July and August, Gallup said.
Because Gallup reviewed data, no one was surveyed and no margin of error was available.