The opposite occurs at each pole in December, when the Northern Hemisphere sees its shortest day and longest night of the year. As the Earth rotates on its axis, the North Pole experiences 24 hours of daylight, while the South Pole is obscured in darkness. The sun's direct rays reach their northernmost position with respect to Earth's equator, along the Tropic of Cancer, at 23.5 degrees north latitude.
Thus, the summer solstice in the Northern Hemisphere is the exact moment each year when this region of Earth reaches its greatest possible tilt toward the sun. The solstices mark when the sun reaches its most northerly or southerly position relative to the Earth’s equator. This tilt means the two hemispheres are exposed to different sun angles and variable lengths of daylight throughout the year. The seasons change at various times of the year due to the planet’s axial tilt of 23.5 degrees as it orbits the sun.
The summer solstice - the longest day and shortest night of the year - occurred at 5:14 a.m. June 21 marked the official start of astronomical summer in the Northern Hemisphere.
