What day does summer begins in the US?

Answer 1

In the Northern Hemisphere, summer begins on the day of the summer solstice, June 21st.

Of course, because the Southern Hemisphere is pointed away from the Sun at this time, June 21st is the first day of winter there.

Answer 2

The start of summer is scheduled to begin at summer solstice which is also called June solstice. Summer solstice is usually called the longest day of the year, meaning the longest amount of daylight in a day. That is not the official definition, but it is close enough for most of us.

In recent history, summer solstice has started around June 20 to June 22 in the Georgian calendar. (The calendar that most of the world uses today.)

Technically there is a particular moment each year when the tilt of the Earth's axis of rotation is perfectly aligned so it is at its maximum tilt towards the sun and therefore the top portion (summer solstice) or bottom portion (winter solstice) of the earth gets the maximum amount of illumination from the sun.

According to timeanddate.com, "The June solstice occurs at 17:16 (or 5:16pm) Coordinated Universal Time (UTC) on June 21 in 2011." At the other end of the process, winter season in the Northern hemisphere begin with December solstice. The arrival of winter solstice has a similar variation of a couple of days.

According to timeanddate.com, "The December solstice will occur at 05:30 (or 5:30am) Coordinated Universal Time (UTC) on December 22, 2011"

Fortunately governments and calendars are usually in agreement, but it can always happen that some group or country decides that summer season starts at a time different than the astronomical definition.

Answer 3

June 21st