Although children have been on vacation for weeks and temperatures have already tipped over 100 degrees, today is officially the first day of summer. This year the first day of summer, also known as summer solstice, falls on June 21, but that day is not the set date every year.
According to Weather.com, “Meteorologically speaking, summer has already started since atmospheric researchers consider June 1 as the first day of the summer season. But astronomically, the summer solstice… will arrive Saturday, June 21, 2014 at 6:51 a.m. EDT.”
The site explains that the change of seasons can be attributed to the tilt of the earth's axis and its revolution around the sun.
In summer, the northern hemisphere receives the most direct sunlight because it is tilted toward the sun. Today, the sun's rays will be located directly overhead at the Tropic of Cancer, a line of latitude located at 23.5 degrees north of the equator.
Summer solstice regularly occurs between June 20 and 22.