First Day Of Summer 2025 Calendar Date In Usa. This is the longest day of the year and marks the start of summer in the northern hemisphere. The first day of summer (june solstice) is when the sun is in its most northern position directly over the tropic of cancer.
The first day of summer arrives with the solstice this year on thursday, june 20, 2025 at 4:51 p.m. The celestial event signifies the first day of winter,.
