That sounds like it's enough water, and at the right frequency when rains are lacking, but it's hard to say for certain. The best way to tell is to feel the soil about six inches deep in the tree's root zone, and water thoroughly once it gets somewhat dry to the touch at that depth. If not too hard to revisit the site, you can check the day or two after watering to see how well the volume of water applied percolated into the root zone by performing the same test. If the soil is damp to the touch six inches down after your soaking, then you can assume it's a good amount of water and more is not needed per watering session. How deeply a watering percolates will depend on soil type (sandy, how much organic matter it contains) and grade.

Given the weeping nature of their branches, willow foliage doesn't tend to noticeably wilt the way other trees and shrubs can when they get too dry, and wilting alone isn't a reliable measure of soil moisture, since over-watered plants can also wilt. (Willow, being more moisture-loving, is much less likely to wilt from being too wet, but it's a good general guideline for other species.) The soil probe test is the more reliable way to judge when watering is needed, especially before wilting is observed, which means the plant is already under stress that might be killing fine roots or increasing its vulnerability to organisms (borers, certain fungi, etc.) that preferentially attack stressed trees.

Miri

For a tree that young, either spot is probably fine, but in general, closer to the dripline (both for ease of probing, and for where most of the feeder roots will be as the tree grows).

For drought status, one useful resource is the U.S. Drought Monitor map, which can be drilled-down to state level (click on the northeastern region, then click on Maryland). Today, for example, the map does show that some eastern portions of the county are in "abnormally dry" status.

Miri