What is Summer Solstice?
June 20-21 is a very important day for our planet. June 20-21 is one of two solstices, days when the rays of the sun directly strike one of the two tropical latitude lines. June 21 marks the beginning of summer in the northern hemisphere and simultaneously heralds the beginning of winter in the southern hemisphere. In 2010, the solstice occurs and summer begins in the Northern Hemisphere summer http://0.tqn.com/d/geography/1/G/3/4/1/81013974.jpgbegins early on June 21, at 7:28 a.m. EDT (11:28 UTC).
The earth's axis is tilted somewhat off the plane of the earth's revolution around the sun. The tilt of the axis is 23.5 degrees.
When the axis tilts towards the sun, as it does between June and September, it is summer in the northern hemisphere but winter in the southern hemisphere. Alternatively, when the axis points away from the sun from December to March, the southern hemisphere enjoys the direct rays of the sun during their summer months.
June 21 is called the summer solstice in the Northern Hemisphere and simultaneously the winter solstice in the Southern Hemisphere. Around December 21 the solstices are reversed and winter begins in the northern hemisphere.
When summer occurs in a hemisphere, it is due to that hemisphere receiving more direct rays of the sun than the opposite hemisphere where it is winter. In winter, the sun's energy hits the earth at oblique angles and is thus less concentrated.