I need gardening istance!?

I live in the Lower Alabama region, and this time of year it is especially hot. We haven't had a lot of rain either. Over the past couple of weeks, my tomato plants have started to die. The branches are turning yellow and the leaves are wilting. I was trimming off the dead branches, too. I water them a couple of times a day, and nothing seems to be helping. My cuber plants seems to be doing well. Can anyone offer any advice?