I think it's OK once soil temperatures get above 50F to plant gourds and melons.

I just planted my potted angled luffa plants today.

I would say: Go right ahead !

Ground temperature is normally over 60F.
If day temp is, say, 75 and night 50F, the ground temperature should be over 60F at night.

For warm weather crops( squashees, melons, egg plants, peppers, tomatoes) when night temps stay about 43F, it is ok, if day temps are over 63F.(roughly).
If night and day temps are slightly lower, the plants will just sit there and do nothing. in 30s might become cold stressed.

You can use some plastic mulch to warm the soil up a bit if you are afraid that the soil is too cold. My luffa seedlings seem to be thriving in the ground after 3 days.

Thank you all. Planted them a week ago.
Eggplants are growing with bigger.But my Okras are staying still doing nothing. I have to wait and see.