First Day Of Summer 2025 Calendar. June 21st, 2025 is the official start date of the summer. Usually, when we talk about the first day of summer, we are referring to the astronomical summer which is defined by the earth's axis and orbit around the sun.

In the southern hemisphere, it will occur on december 21, 2024. Find out the date when summer is in 2025 and count down the days until summer with a countdown timer.