Depends on the type of pumpkins that you are planting. Mine have been growing since the beginning of May but then again I am looking for a 100 +lbs pumpkin. I would think that you could still do a smaller type but you better hurry and better start with a plant not a seed.
Depending on your zone you should have enough time. Right now I guess everyone at zone 4b and up can safely grow pumpkins without any problems. That's assuming the average frost dates hold up.
Try a early season variety. Most pumpkins take at least 90 days to harvest but can be left on the vines to cure through a frost.
I'm in Michigan too and I just planted some pumpkins I got for free from the nursery (they were going to be thrown out cus they are little brown) I think I can bring them back to health. I've never had pumpkins before though...so we shall see.