Querying in the summertime?

Is July typically a month in which agents take vacation?

I just send out another round of queries last week, and, oddly, I haven’t heard any responses yet.  I mean, many agents take several weeks to respond, of course, that’s normal.  But typically, in any batch of ten or so, there are a couple who turn it around in 48 hours, though usually with a rejection.

Not that I’m in a big hurry to get rejections, mind you.

Of the queries I have out there, there are three who are currently closed to new queries; a planned, temporary closure from July to September in all three cases.  I find this fascinating.  Is summer the unusually heavy time for querying?  Or is it that three months of closure is necessary to be able to take a mere two weeks of vacation?