First Day Of Summer 2025. Summer begins with the solstice on thursday, june 20, 2024, marking the astronomical first day of summer in the northern hemisphere. The summer solstice marks the official start of astronomical summer and the longest day of the year.
This day is also known as the summer solstice. Summer begins with the solstice on thursday, june 20, 2024, marking the astronomical first day of summer in the northern hemisphere.