The 2023 summer solstice occurred on Wednesday, June 21 at 10:57 a.m. Eastern Time, marking the longest day and shortest night of the year, as well as the first day of astronomical summer in the Northern Hemisphere. The summer solstice is the exact moment each year when the hemisphere reaches its greatest possible tilt toward the sun. The sun's direct rays reach their northernmost position with respect to Earth's equator, along the Tropic of Cancer, at 23.5°N latitude.
At the same time in the Southern Hemisphere, the winter solstice occurred when the hemisphere reached its greatest possible tilt away from the sun, marking the shortest day and longest night of the year.
The GeoColor animated imagery in this video was created by collecting one image per day over the last year from GOES East (GOES-16), taken at 1200 Coordinated Universal Time (UTC), and looped together. The resulting animations show how the Earth’s seasons change from equinox to solstice due to the planet’s 23.5-degree tilt.
Although the amount of solar radiation reaching Earth peaks during the summer solstice in the Northern Hemisphere, temperatures for most of the United States (and other countries north of the equator) tend to keep increasing into July. The temperature increase occurs because the rate of heat input from the sun during the day continues to be greater than the cooling at night for several weeks–a phenomenon known as seasonal lag. Not until late July and early August do temperatures slowly start to descend.
Notice in this image how the shadow that separates day and night across Earth is highly slanted. That shadow is called the daylight terminator. As the Earth rotates on its axis, the North Pole experiences 24 hours of daylight, or “midnight sun,” while the South Pole is obscured in darkness. The opposite occurs at each pole in December when the Northern Hemisphere sees its shortest day and longest night of the year.
The amount of daylight we see depends on our distance from the equator. For example, in Fairbanks, Alaska, the sun rose today at 2:59 a.m. and will set at 12:47 a.m. tomorrow. In Miami, it rose at 6:30 a.m. and will set at 8:16 p.m