i'm in NE PA and my brassica mix of choice is modeled on Lick Creek's. PTT, DER, GHFR. I'm a little south of you, but i'm also in an area of higher elevation that is generally colder than the surrounding area. I have planted that brassica mix as early as July 7th and as late as August 8th. The early side saw the radishes start to bolt before bow season opened, but the other two components were pretty much good to go....some of the PTT began to rot out a little later into October. I had some pretty huge tubers and lots of green top growth though. The later side the tubers didnt amount to much...hot dog sized radish and golf ball sized turnips...but sufficient green top growth. I really like to shoot anywhere in the July 12th to July 20th window....but if i cant get them in during that window...i still feel pretty good about July 21st to August 1st. Of course weather conditions can make any of these date ranges mean nothing.