Summer 2024 Months In Usa. The longest day of summer is the summer solstice, which marks the first day of astronomical summer. This year, the first day of summer, also known as the summer solstice, is thursday, june 20.

Seasons divide the year into four distinct periods of time named spring, summer, autumn/fall, and winter. Generally, the break begins in late may or early june and concludes in late august or early september.