* The summer solstice is the day with the longest period of daylight and the shortest night of the year. It occurs when one of the Earth's poles has its maximum tilt toward the Sun. * On 21st June, the summer solstice occurs in the Northern Hemisphere. This is the longest day of the year for that hemisphere. * The Arctic Circle, which is in the Northern Hemisphere, experiences continuous daylight throughout this day. This is because the tilt of the Earth's axis is such that the North Pole is facing towards the Sun. * Therefore, the Sun does not set below the horizon at the Arctic Circle on this day.