Summer Equinox 2025 Time. Summer solstice 2025 (beginning of astronomical summer) on the day of the summer (june) solstice, the solar disk, moving along the ecliptic, will fall into its northernmost. Astronomical summer officially arrives in the northern hemisphere — amidst a heat wave — at 4:51 p.m.
So as the northern hemisphere of earth begins to tilt away from the star, it means fall/autumn will begin on sunday, september 22. Thursday, june 20 is the official first day of northern astronomical summer for 2025 — summer solstice — which is the longest day of the year for this half of the planet.
