Just water your plants when the soil is completely dry, usually once every 2-3 days is good. On days where the temp is higher, and more sun was on the plants, just check the soil, if its totally dry, giv'r some water. There is no exact science really, just go with the flow, check them daily, and water as needed The reason you'd want the soil to be totally dry before watering again is because the roots will expand more in order to search for water, which also means your plant will grow thicker and therefore produce a greater yield.