It's a bit counter-intuitive, since there is so much water in the fruit, but the more you water them after they start setting on the smaller and less flavorful the melons will be. Any time we have wet weather in July and August (rare), my melons are practically inedible. Drought years are the best.
In general, melons thrive on benign neglect. They do benefit from watering and weeding when the vines are first developing. Beyond that, the more you care for them the less happy you are likely to be with the results.
