Something tells me you live in the southern half of the U.S.

Your cherry tree will greatly benefit from some partial shade in the hot Summer months.

Make sure the soil is kept moist, but at the same time, make sure the roots are not drowning in water. Ideally the soil should be moist, but not muddy. If the roots are sitting in a pool of water, that can cause yellowing and loss of the leaves also.

I suspect the main problem, however, is too much heat and sunlight. If the temperature is too high, the tree may suffer from dehydration, regardless of how much water is in the ground. More moisture in the soil can compensate for higher temperatures only up to a point. In colder climates, cherry trees love full sun, but the same is not always true in warmer climates.

You might consider getting a shade tarp to filter out some of the sunlight (preferably a white colored one if the tarp is going to be right up against the tree, because black absorbs heat). Another strategy, if you live in a dry climate (like the Southwest), is to mist the leaves during the middle of the day, but do not do this if you live in the hot humid South, because that is going to cause your cherry tree to succumb to a quick death from disease.

As you have probably been able to surmise, cherry trees can be very finicky and need different treatment depending on what type of climate they are growing in.