Watch the amount of sunlight reaching the North Pole increase with the coming summer solstice in this animation of GOES-16 visible imagery!
The summer solstice -- the official start of astronomical summer in the Northern Hemisphere -- occurred at 12:24 am (EDT) today, June 21, 2017!
The term "solstice" refers to either of the two times per year when the sun is at its greatest angular distance from the equator: about June 21 (the Northern Hemisphere summer solstice), when the sun reaches its northernmost point, or about December 22 (the Northern Hemisphere winter solstice), when it reaches its southernmost point. s a result, today will be the longest day of the year in the Northern Hemisphere.
Of course, "astronomical" summer is not to be confused with "meteorological" summer, a term used by meteorologists and climatologists, who break the seasons into three-month periods based on the annual temperature cycle and the calendar. We generally think of winter as the coldest time of the year and summer as the warmest time of the year, with spring and fall being the transition seasons, and that is what the meteorological seasons are based on. Meteorological spring includes March, April, and May; meteorological summer includes June, July, and August; meteorological fall includes September, October, and November; and meteorological winter includes December, January, and February.
On the contrary, the natural rotation of Earth around the sun forms the basis for the astronomical calendar, in which we define seasons with two solstices and two equinoxes. Earth’s tilt and the sun’s alignment over the equator determine both the solstices and equinoxes. Therefore, astronomical summer runs from today, June 21, 2017, to September 22, 2017.