First Day Of Each Season

Seasons are caused by the earth's revolution around the sun and the Earth's axis being tilted. In polar and temperate regions, the different seasons are characterized by the transformation of the sunlight's intensity that reaches the surface of Earth.
There are two remarkable seasons for tropical regions--- rainy and dry season. In polar and temperate regions, spring, summer, autumn and winter are the four different seasons.
Spring Equinox
It is also known as the first day of spring or March equinox. It marks the start of spring season in the northern part of the hemisphere and the start of autumn in the southern part. The Spring or March Equinox happens when the sun moves to the equator from south going to north. This may happen some time on March 20 or the next day every year. During this season, day and night are equally distributed within the day every place in Earth.
Here are the first days of spring for the coming years:
March 20, 2010
March 20, 2011
March 20, 2012
March 20, 2013
March 20, 2014
March 20, 2015
March 20, 2016

Summer Solstice
It happens when the earth's axis is tilted in a way that it is closest to the powerful sun. For people who live in higher latitudes, summer solstice is known as the longest day of the year.
Here are the firs days of summer for the coming years:
June 21, 2010
June 21, 2011
June 20, 2012
June 21, 2013
June 21, 2014
June 21, 2015
June 20, 2016
Fall Equinox

It is also known as the first day of autumn or autumnal equinox. During an autumnal equinox, the Sun crosses from north of the equator going to south. This happening indicates the start of fall in the northern part of the hemisphere and the start of spring in the south. Since it occurs every September, it is also known as September equinox. Sub-solar point is the place on earth where the sun is straightly above our heads at mid noon. Sub-solar point takes place during the March and September equinox.
Here are the firs days of autumn for the coming years:
September 23, 2010
September 23, 2011
September 22, 2012
September 22, 2013
September 23, 2014
September 23, 2015
September 22, 2016

Winter Solstice
It reminds everyone that winter is coming. The occurrence of Winter Solstice happens when the earth's axis is tilted in a way that it is positioned farthest away from the powerful sun. For people who live in higher latitudes, the season has the longest night and shortest day.
Here are the first days of winter for the coming years:
December 21, 2010
December 22, 2011
December 21, 2012
December 21, 2013
December 21, 2014
December 22, 2015
December 21, 2016
In ecology, different seasons affect the behavior of animals and plants. There are events that can only happen on a particular season. Some animals migrate or hibernate and plants become dormant during winter and flowers bloom during spring season.