In 2016, Summer Solstice begins June 20

from ALMANAC dot-com (Old Farmer's Almanac online article):
The summer solstice heralds the beginning of summer in the Northern Hemisphere. The timing of the summer solstice depends on when the Sun reaches its northernmost point of the equator.
In 2016, summer begins with the solstice on June 20 at 6:34 a.m. EDT / 7:34 a.m. Central Time.
The word solstice is from the Latin solstitium, from sol (sun) and stitium (to stop), reflecting the fact that the Sun appears to stop at this time (and again at the winter solstice).
In temperate regions, we notice that the Sun is higher in the sky throughout the day, and its rays strike Earth at a more direct angle, causing the efficient warming we call summer.
This summer solstice is the day with the most hours of sunlight during the whole year.