Summer Solstice 2025

Summer solstice, the astronomical beginning of summer, occurs after the Sun sets on Friday, June 20, 2025, at 10:42PM EDT. Solstice is Latin for “Sun Stand Still.” This came from the observation that the Sun’s position appears to stop or stand still in the days surrounding the solstice.  For those of us in the northern hemisphere, the summer solstice marks the longest day and shortest night of the year.  This apparent change in the position of the sun is due to the 23.5-degree axial tilt of the Earth and our orbital movement around the sun.  This is the reason we have seasons. The solstice occurs at the specific moment the Earth’s north polar axis is at its maximum tilt toward the Sun.  At this moment, the Sun is directly over the Tropic of Cancer.  And regardless of where you live the solstice happens at the exact same moment for everyone on the planet. 

Ancient cultures watched and studied the Sun’s path across the sky.  They understood that the Sun’s position along the horizon at sunrise and sunset moved in a regular and predictable way during the year.  They also knew that the amount of daylight also changed in a predictable way through the year.  Many of these cultures built monuments to align with the solstices.  We are familiar with Stonehenge built around 3000B.C. by the early neolithic people in England.  On the Summer solstice the Sun rises directly over the Heel Stone.   Ancient Native Americans also used rock to mark the solstice.  On Fajada Butte behind three stone slabs Ancestral Puebloan people in Chaco Canyon, New Mexico, carved two spiral petroglyphs into the rock – a large one and a small one.  Late morning on the summer solstice the sun shines on the three stone slabs creating a spot of light directly above the large spiral.  During the next 15 minutes this spot of light stretches into a shaft of light called a “sun dagger” that goes through the middle of the spiral and gradually moves down the spiral and disappears.  Knowing when the summer solstice occurred was important to ancient cultures because it marked the longest day of the year, it marked the transition from planting season to the growing season for crops and with more sunlight and warmth it promised the abundance of nature.

Celebrate the summer solstice! Join us on June 20, 2025, from 9:00PM-11:00PM for our summer solstice night hike. After the hike, weather permitting, join the Astronomy Club in TWC’s observatory to enjoy the solstice night sky through our telescopes.  If the weather doesn’t cooperate there will be a Tonight’s Sky program in the planetarium.