Discover the astronomical date, solar declination, and maximum daylight duration for the longest day of the year (Summer Solstice, ~June 20–21).
The astronomical summer solstice marks the moment Earth's axial tilt reaches its maximum inclination toward the Sun in this hemisphere.
During the summer solstice, Earth's rotational axis is tilted by 23.44° toward the Sun. In the Northern Hemisphere, this brings the Sun directly overhead at the Tropic of Cancer (23.5° N latitude), producing the longest period of daylight and the highest solar altitude of the year.
Regions north of the Arctic Circle experience 24 hours of continuous sunlight (Polar Day).
When the Northern Hemisphere experiences the summer solstice in June, the Southern Hemisphere experiences its winter solstice (shortest day).