I don' think any of those will actually die at 38 degrees.

They will stop growing until it warms up again.

This is what I use for my tomatoes. I have hoops of pvc pipe and I throw a sheet of clear plastic over the hoops. That holds the plastic up off the plants. If it is going to be really cold, I burn a 100 watt bulb inside the plastic tent.

Before I had the hoops and the plastic, I saved many a tomato by setting a couple of 30 gallon trash cans beside them and throwing a canvas tarp over the can and the tomato. That kept the frost off of them. Of course, the tarp had to be removed each morning.

If you need to cover tomatoes, you'll have to cover the peppers at the same time. I think they are even more sensitive to cold.

I saw on a website, can't vouch for it, to put a gallon jug of water next to each plant to be heated by the sun, this is supposed to warm your plants at ngiht.

I doubt this, but others may be able to add more about it.

Where are you that it's gonna get that cold?

Personally, I wouldn't worry about any of them. If it rains...that'll help.

It'd take a few hours of 32 degrees to do much damage, at this stage.

The tomatoes and melons/vining crops are the most sensitive. They will take 38F but not much below 32F. Melons might die from the cold soil unless it warms up soon.

thanks everyone!
It was 36 degrees but the sun was shining when I checked. I don't think it froze. It never rained. I covered everything to be safe except for the potatoes. Ran out of covers so I put pine needles over the vine seedlings. Last fall we had frost when it was 38 degrees so I didn't want to take any chances.
forpityssake: I am in the mtns of Idaho but elevation is 3000'