Take the dates to maturity on your seeds, and add 14 days. (Plants grow slower in the shorter days of fall) If you dont know the days to maturity, on most pumpkins I believe it is 100- 120 days.
Count back that long from your last frost date, and see if it is aaround now, or if it is too late already. You may still be able to get them in, since they would get a fast start in the warm days of summer.
There is no way I could plant them now, I live in zone 5. You maybe would still be able to though. You could also plant a fast growing winter squash, I think acorn squash mature in 80-90 days.