Just water them on schedule.
They all kind of wilt at mid day but then perk up.

Actually, when they get used to too much water behave more like that .. spoiled..hehe

This post was edited by seysonn on Tue, Aug 20, 13 at 1:29

In addition to what seysonn said I would check for Squash Vine Borers (SVB) If you are not familiar, the moth (really looks more like a weird wasp/bug that is black and dark red than a moth) flies around and lays eggs at the base of your vines. When the larvae hatch they bore into the vine leaving a hole and a dark orange "frass" that looks a bit like saw dust. The borer travels in the hollow center of the vine and chews it way through closed areas cutting off water circulation in the vine. There are many remedies for this none of which are easy. I am very diligent early in Spring to check the vine at and just below soil level for small brown seed like eggs and remove them. If they are already attacking your plant then as I said earlier there are many methods there also. I am sure there are threads here on them or check youtube. If you think this is your case post as such and I can give some advice also. Good luck and hopefully you have an awesome harvest!