When Does Summer Start 2025 Usa 2025. In 2025, the summer solstice will occur on june 21, at 02:42 gmt in the northern hemisphere, and on december 21, 2024 at 09:20 gmt in the southern hemisphere. The longest day of 2025, also known as the summer solstice, is friday, june 20.

How many days until summer 2025? Deadline to confirm your spot and submit.