 If the leaves are curling or if they're wilting, and yes, in the real heat, tomato leaves will curl because they're trying to conserve moisture. But in the late afternoon and early morning, they should be flattened back out, absorbing the full leaf view of the sunshine. In the opposite, you know, you can overwater and then the leaves will turn yellow. And then if they've turned yellow, you pretty much know that you're drowning the roots properly.