Summer Begins in Northern Hemisphere
This full-disk image from NOAA’s GOES-13 satellite was captured at 7:45 a.m. EDT (11:45 UTC) and shows the Americas on June 21, 2012, the start of astronomical summer – in the Northern Hemisphere – that year.
The first day of summer in 2025 is June 20; it is also the longest day of the year. In the Southern Hemisphere, it’s the shortest day of the year and the beginning of winter.
Earth orbits at an angle, so the Northern Hemisphere is tilted toward the Sun half of the year — this is summer in the Northern Hemisphere, and winter in the Southern Hemisphere. The other half of the year, the Northern Hemisphere is tilted away from the Sun, creating winter in the north and summer in the south. Solstices happen twice per year, at the points in Earth’s orbit where this tilt is most pronounced.
Image credit: NASA