First And Last Day Of Summer 2025 Calendar. Find out the date, how long in days until and count down to till summer 2025 with a countdown clock. The first day of summer is also known as the summer solstice, and in 2025 it happens on thursday, june 20 at 4:51 p.m.

Learn more about when it starts, the summer solstice and more. When does summer start in 2025.