What is the summer solstice?

The Summer Solstice: Just the Facts The summer solstice is the day the Sun travels the longest path through the sky. The summer solstice is considered the first day of summer. It occurs on June 20 or 21 in the Northern Hemisphere... ...and December 21 or 22 in the Southern Hemisphere. Summer lasts until the autumnal equinox. Equinoxes occur when the Sun is directly above the Equator and day and night are of equal length. In either hemisphere, the summer solstice is the longest day of the year, when the Sun’s apparent path is the farthest north or south from Earth’s Equator. The Summer Solstice is celebrated in many cultures, including those of Scandinavia, which observe Midsummer’s Eve as a holiday.