On a hot, windy day, the surface will dry out even if the ground is saturated. The best way to judge the water needs of a plant is to first learn a little about the type of plant you are growing. Some are very drought tolerant. Others require consistently moist soil. Next, judge the situation where it will be growing.
Sandy soils have very little capacity to hold moisture and dry out quickly between waterings.
Soils with lots of organic matter have good moisture retention. Clay soils have good moisture retention but may hold too much water. Sloped soil drains much more quickly. You will also need to judge the plant's general condition. A healthy plant with an established root system will be much less demanding than one that is newly planted or one that is already struggling.