First Day Of Summer 2025 Date Countdown. Et on june 20, 2025, accordi n g to space.com. That also happens to be the summer solstice, aka the start of summer.
This year the summer will start on thursday june 20, 2025 (day of the summer solstice) and will end on sunday september 22, 2025 with the autumnal equinox. The first day of summer is 20 june 2025.