I was born in June but my middle name is May. :P
I've only met one June. I can see it on a lot of ages. I think my first exposure to June as a name was Junie B Jones-- at least I assumed Junie was short for June. And is there a character in something called "Aunt June"? Those two associations make it seem like it could easily be young or old to me. And I know Juniper is fairly popular and that has June as a nickname. Juno is also maybe getting popular?
I've met one January (and it was a translation). I could see it being more popular if "Jan" comes back as a desirable nickname.
I think Mae looks more "vintage" than May so that could be why it's making a comeback. Not sure why May isn't still popular though, it seems more neutral than Mae. Still cutesy but not so specific.
I'm surprised April isn't still popular.
I could see March being a popular middle name after the month and Little Women.
I've definitely met several Augusts, all boys. (Lots of girls named Autumn though. The "Gus" part of August sounds boyish.)
July seems like it should be a name because of Julie, Julian, Julius, etc. but I guess the "ly" ending makes it too 'monthy' and not enough 'namey'?
I could see any of the -ember months being a middle name. Also October. As first names they'd need a nickname (Nova, Ember, Deci) but even then I'd prefer them as middle names since they're so wordy.