This year, mid-June was a bit late (normally it's right on time, for the frost) but this year I'd sprained my left knee on April 2nd (just missed April Fools!) and I wasn't able to get down to plant until mid-June. No (before you ask), I don't have the option of planting in raised beds. It's a new garden created this year at our friend's place as we don't have enough room for a garden in the back yard (and it's at a slope so all the watering runs off, out of the yard).
I live in an extremely small home (no basement or 2nd floor) and don't have room to put many plants in the house to start them. I only have the option of planting in pots on our deck (16'x19') and in our friend's yard.
Also, before mid-June, there's no guarantee of no snow or frost. One year we had a blizzard 2 days before the end of May! There was so much snow that tree branches were breaking all over the city! This year however, was perfect weather mid-May and would have been a good year to plant then. If only I hadn't hurt my knee.......