Summer solstice 2023 marks longest day in the Northern Hemisphere as Earth's seasons change

Sun rises above new york city skyline on summer solstice, with a bird flying above.

Summer officially began in the Northern Hemisphere today (June 21), marking the longest day of the year. 

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, according to Chris Vaughan, amateur astronomer with SkySafari Software who oversees Space.com's Night Sky calendar.