If plants are in the ground and not in pots they may survive the summer heat with as little as one deep watering a week. If the soil is rich and full of organic matter it acts like a sponge to hold moisture especially when there is a mulch on top. I like to look at the plant and if I detect wilting or a dull green look to the leaves I will dig down and see it the soil is moist two inches below the top of the soil. Clematis and delphiniums need more water than most perennials so you may want to hand water these two plants twice a week. Keep growing, Marianne Binetti