The summer solstice occurs when a planet's rotational axis, or geographic pole on either its northern or its southern hemisphere, is most inclined toward the star that it orbits.  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° in the Northern Sky and −23.44° in the Southern Sky.)  This happens twice each year (once in each hemisphere), when the Sun reaches its highest position in the sky as seen from the north or south pole.

Worldwide, interpretation of the event has varied among cultures, but most recognize the event in some way with holidays, festivals, and rituals around that time with themes of religion or fertility.  In some regions, the summer solstice is seen as the beginning of summer and the end of spring.