When Is 2025 Summer Solstice. Is the solstice the longest day of. The longest day of the year falls on either june 20 or 21 every year in the northern hemisphere.

This happens around june 21 each year. 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.