The summer solstice, an astronomical event, signifies the onset of summer and the Northern Hemisphere's longest day of the year. It occurs when the sun is directly positioned over the Tropic of Cancer, located at 23.5 degrees north latitude.

Typically falling on June 21, the summer solstice can also occur on June 20 or June 22, depending on the year and time zone. On June 21, the sun remains continuously above the horizon, never setting below it at the Arctic Circle.