When Is The First Day Of Summer 2025 Date. This is the longest day of the year and marks the start of summer in. This year the summer will start on thursday june 20, 2024 (day of the summer solstice) and will end on sunday september 22, 2024 with the autumnal equinox.

This is the longest day of the year and marks the start of summer in. 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 its furthest tilt and begins to change directiion back.