The best way to know if your tree needs water is to check the ground below it.
One way to do this is to dig down along the root ball to check the consistency of the ground. If you discover that it’s cool to the touch and has a soft play-dough like feel, you’re in good shape. If the dirt crumbles in your hand, it’s time to water.
Another way to check the soil is to take a long screwdriver (4 inches or longer) and poke it into the ground about 10 inches from the trunk. If the ground is moist, the screwdriver will go in pretty easily. If you can’t poke it in easily at least 6 inches, it’s time to water.