Final answer:
The Sun can be at your zenith during some part of the year only if you are located between the Tropic of Cancer at 23° N latitude and the Tropic of Capricorn at 23° S latitude. This happens at the Tropic of Cancer during the summer solstice and at the Tropic of Capricorn during the winter solstice. At the equator, the Sun is at the zenith on the equinoxes.
Step-by-step explanation:
The locations on Earth where the Sun can be at your zenith during some part of the year are restricted to areas between the Tropic of Cancer, 23° N latitude, and the Tropic of Capricorn, 23° S latitude. Specifically, on or about June 21, which is the summer solstice in the Northern Hemisphere, the Sun shines most directly on the Tropic of Cancer, allowing it to be at the zenith at noon for those locations. On the equator, the Sun can be at the zenith on the vernal and autumnal equinoxes, which occur around March 21 and September 21. However, locations beyond these latitudinal boundaries will never experience the Sun at the zenith.
During the winter solstice, which occurs on December 21, the Sun is at about 23° S, directly overhead at the Tropic of Capricorn at noon. In the Northern Hemisphere during this time, such as a place on the Tropic of Cancer, the Sun would have an altitude of 44° at noon, which is the result of subtracting the declination difference (46°) from 90°. It is important to note that how high the Sun gets above the horizon is season-dependent, reaching its highest point at mid-summer and the lowest at mid-winter.