The summer solstice, also known as
festival solstice or midsummer, occurs when one of the Earth's poles has its
maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere
(Northern and Southern). For that hemisphere, the summer solstice is when the
Sun reaches its highest position in the sky and is the day with the longest
period of daylight. Within the Arctic circle (for the northern hemisphere) or
Antarctic circle (for the southern hemisphere), there is continuous daylight
around the summer solstice. On the summer solstice, Earth's maximum axial tilt
toward the Sun is 23.44°. Likewise, the Sun's declination from the celestial
equator is 23.44°.
The summer solstice occurs during
summer. This is the June solstice in the Northern Hemisphere. Depending on the
shift of the calendar, the summer solstice occurs sometime between June 20 and
June 22 in the Northern Hemisphere.
Cultural significance
Since prehistory, the summer
solstice has been seen as a significant time of year in many cultures, and has
been marked by festivals and rituals. Traditionally, in many temperate regions
(especially Europe), the summer solstice is seen as the middle of summer and
referred to as "midsummer". Today, however, in some countries and
calendars it is seen as the beginning of summer.
Longest Day
Although the summer solstice is the longest day of the year for that hemisphere, the dates of earliest sunrise and latest sunset vary by a few days. This is because the Earth orbits the Sun in an ellipse, and its orbital speed varies slightly during the year.