Summer Solstice

In this year, 2011, summer begins in the Northern Hemisphere on June 21 at 1:16 P.M. (EDT).

"The word solstice comes from the Latin words for "sun" and "to stop," due to the fact that the Sun appears to stop in the sky. The Sun is directly overhead at its most northern point at "high-noon" on the summer solstice, creating more sunlight in the Northern Hemisphere on this day then any other." (thanks Farmer's Almanac!)

"The summer solstice occurs exactly when the Earth's axial tilt is most inclined towards the sun, at its maximum of 23° 26'. Though the summer solstice is an instant in time, the term is also colloquially used like Midsummer to refer to the day on which it occurs." (thanks Wikipedia!)