The summer solstice in the Northern Hemisphere is the day when the sun is farthest north. In 2014, this occurs on June 21 at 5:51 a.m.
As Earth orbits the sun, its axis of rotation is tilted at an angle of 23.5 degrees from its orbital plane. Because Earth’s axis of spin always points in the same direction — toward the North Star — the orientation of Earth’s axis to the sun is always changing as Earth orbits around the sun.
As this orientation changes throughout the year, so does the distribution of sunlight on Earth’s surface at any given latitude. The summer solstice is the day of the year with the most daylight in our hemisphere.
On the Northern Hemisphere’s summer solstice, the northern spin axis is tilted toward the sun and latitudes north of the Arctic Circle (66.5 degrees N) have 24 hours of daylight.
The length of daylight is related to how high the sun gets in the sky. At the summer solstice, the sun reaches its highest point in the sky and so daylight is longest.
Our earliest sunrise, however, occurred Saturday, while our latest sunset occurs about a week later than the summer solstice. So, while the summer solstice has the longest daylight hours, that day does not correspond to the earliest sunrise or the latest sunset. The reason that the earliest sunrise and latest sunset do not occur on the summer solstice is a combined effect of the tilt of Earth’s axis and the elliptical path of Earth around the sun.