Well, to my understanding, the cucumbers are very sensitive to frost whereas the squash and pumpkins are a little hardier.
Now, I say this because I planted cucumber sets last May and a light frost came and killed them off. I also planted some squash (butternut), in the late summer (I don't think I ever really believed that I would get anything from them, but why not) and they were killed by the fall frost.
The reason I say the the squash are probably a little hardier is that they look that way.
Jal has a good idea; plant early and if you don't get a frost, great
, if you do, just re-plant
. If you don't have a lot of seeds, plant half early and the other half later.
For the pepper transplants, you want to make sure that the soil is warm and there is no danger of frost. If you plant peppers in cool soil, you man stunt their growth for the whole season.
I don't have any experience with eggplant (yet
), but I do know that they, too, like it hot, so I'm not putting mine in until I put the peppers in. Put it this way, the last frost date is May 16; the peppers and eggplants are going in June 1.
Oh, here's a thought, you could help your soil to warm up by using some black plastic a week or so before you plant and could keep it warm by using low-tunnels.
I hope this helps you out.