I don't know when your autumn ("fall") or summer are in relation to September. Don't mix keys here, either use months or quarters, not a mix of things including some relative to a specific hemisphere.
If you're reading it from a southern hemisphere viewpoint and find that it doesn't make sense, isn't it quite simple to just go, "Oh, perhaps it's the opposite?" and apply that?
This is hardly the first time I've ever encountered this sort of thing. In fact, as an American, I've had to employ this sort of thinking myself when interacting with people on forums from places like South America and Australia.
It's an easy fix, and it's not that big of a deal, honestly - an innocent little side effect of the fact that we're able to communicate at such a global level[1]. :)
You did, in fact, know when was referred to. It's even possible to realize that "over the summer" can include Christmas in Sydney or Buenos Aires! Mostly people realize we live on a sphere, and what the consequences of that are.
† With apologies to American Samoa.
‡ Country name spelled in full to avoid the predictable bellyaching about the existence of a continent of the same name, or two, depending on where you hail from. Another thing you are not in fact confused about.