First Day Of Summer 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. This is the longest day of the year and marks the start of summer in the northern hemisphere.

Is the june solstice the first day of summer? Summer 2025 starts on friday, june 20th in the northern hemisphere, with the first day of summer being the longest daylight day of the year with the earth’s axis having reached.