At the June solstice the midday sun stands directly overhead along a specific line of latitude. The Tropic of Cancer is that line, located at approximately 23.5 degrees north of the equator. It marks the northern boundary of the tropics.

The name comes from the constellation Cancer, in which the sun was located at the summer solstice in classical times. The exact latitude slowly shifts because of changes in Earth’s axial tilt. Along this line the length of daylight reaches its annual maximum in the Northern Hemisphere.

The Tropic of Cancer passes through Mexico, Egypt, Saudi Arabia, India, and southern China, among other regions. It serves as a standard reference in climate classification and in the definition of tropical zones. Crossing it has long held symbolic meaning for travelers.

• Latitude 23.5° north
• Northern limit of the tropics
• Sun is directly overhead at June solstice
• Reference line for climate zones