I'm right on the border of 6a, so some years (probably like this one) we tend to be colder than others. I have a May 1st frost free date but last year we had frost problems until late May.
So this year I planned most of my crops for May 15th frost free.
I'm going to be a little late starting my broccoli since I'm away until next week. I was looking at your thread on broccoli plants and I'll be about a month behind your schedule.