Summer officially kicks off in the Northern Hemisphere today (June 21), marking the longest day of the year. And to our readers in the Southern Hemisphere, welcome to the first day of winter!

During the June solstice (or summer solstice), the sun reaches its highest and northernmost points in the sky. Delivering the maximum daylight hours of the year for the Northern Hemisphere and minimum daylight hours of the year in the Southern Hemisphere.

This year, the summer solstice officially occurred at 5:14 a.m. EDT (0914 GMT), when the sun reached a point directly overhead of the Tropic of Cancer (latitude 23.5 degrees north).

In addition to the longest day of the year and the start of summer, the June solstice also occurs at the moment the northern half of Earth is tilted toward the sun, resulting in the Northern Hemisphere receiving sunlight at the most direct angle of the year.

As always, there are two sides to every story. While the Northern Hemisphere welcomes longer days and warmer temperatures, the June solstice marks the beginning of winter in the Southern Hemisphere when the sun is at its lowest point in the sky.