On June 21st, when the sun is overhead at the Tropic of Cancer,places in the Northern Hemisphere experience

Explanation

June 21st is the summer solstice in the Northern Hemisphere. The North Pole tilts toward the sun, giving more daylight hours.

This is the longest day of the year in the north. Places near the Arctic have almost 24 hours of daylight.

The opposite happens in the Southern Hemisphere, where it is their shortest day.