Here in Ontario, we have seasonal table grapes in the fruit markets in addition to year-round, imported grapes from places like California, South America and South Africa. The first grapes to make it into fruit stands here are invariably the Sovereign Coronations, alternatively known as "Seedless Concord", though I believe that there may actually be a proper variety with that name that's separate from Sovereign Coronation.
Now, normally I've not been a fan of SC over the years; the grape, although it ripens extremely early (mid-to-late August) and is seedless, sometimes suffers from weedy flavours - this I attribute to overcropping. The SC variety is essentially a labrusca/riparia/vinifera hybrid that tastes like Concord when ripe, but can veer off into weedy/wild riparia flavours if underripe.
This year, though, the grapes are just lovely: Dark purple in colour, small, with intensely concentrated Concordy flavour; quite sweet in addition to being tart, and very, very tannic. I can't get enough of them. I almost wish they had seeds so they'd be even more of a tannic treat.
Now, what about your area? We rarely get any other kinds, though there are white seedless hybrids grown for the table here too, such as Himrod - though these are not nearly as often seen as the SC. One year I even managed to snag some Canadice grapes - lovely pink-hued, small, seedless grapes that look like Delaware (which is a seeded labrusca wine grape).