Lol, it's not because of the govt. I suppose you COULD blame it on people being away for the summer, but i speculate the real reason is that its GROWING SEASON.

No body grows big time during the winter, so we won't have lots of tree for summer.
Everyone grows alot during summer, so we have to wait till this harvest is done (around aug, sept)

Or at least that's how it's worked for me and my area.