It's Summer Solstice Time—Here's What to Know

It's hard to believe that a mere six months ago, those of us in the Northern Hemisphere were grimly facing the shortest day of the year—and now suddenly, the sun is setting at bedtime and the unofficial first day of summer is upon us. How did that happen?! The winter and summer solstices sometimes feel out of whack with the seasons they represent—shouldn't the longest day of the year be the hottest and occur at the height of summer? Answers to that phenomenon and others are explained below.

(Note: For the Southern Hemisphere, this is all reversed, thanks to our topsy-turvy world.)

1. When Does the Summer Solstice Happen?

In North America, we can revel in the longest period of sunlight in 2023, on Wednesday, June 21, at 10:57 a.m. EDT (or the equivalent in your time zone). This is the precise moment when the sun stands still at its northernmost point as seen from Earth. Its zenith doesn’t teeter north or south but sits patiently at the Tropic of Cancer before switching directions and heading south again. This is where the word solstice comes from; the Latin "solstitium"—from sol (sun) and stitium (to stop).

2. There Will Be SO MUCH SUNLIGHT

Get your sunglasses out, bare your shoulders, put on the sunscreen! The meteorologists willing, we will have loads of sunlight. In New York City, we will have a soul-affirming 15 hours and 8 minutes between sunrise and set—and add a few hours of light on either end for when dawn actually breaks and darkness descends. (You can check your day length at the Farmer’s Almanac sunrise and sunset calculator, to see what to expect in your neck of the woods.)

3. The Longest Day Isn't the Hottest

Given that the sun passes directly overhead on the solstice—and it's the day with the most sunlight—one wouldn't be off-base to think it might claim the highest temperatures as well. But no. As NOAA explains, in the US, temperatures continue to inch up into July. "The temperature increase after the solstice 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 until temperatures start to descend in late July and early August."

4. The North Gets Short-Changed on Summer Sun

While it certainly may not feel like it, in the Northern Hemisphere’s summer we are actually farthest from the sun thanks to the planet's tilt; we get 7% less sunlight than the Southern Hemisphere does during their summer. Something we'll be grateful for in a few billion years (see #7).

5. Despite the Sunlight, It Was Once a Dark Day for Science

Galileo Galilei strongly supported Copernicus' theory of a heliocentric universe, that the Earth revolved around the sun. For his advocacy of this theory, which went against Catholic church teachings that Earth was the center of the universe, he was accused of being a heretic, among the most serious of crimes. While he was cleared of charges of heresy, he was instructed to no longer espouse the theory. In 1632, he published a book once again promoting the heliocentric theory of Copernicus. And once again he was called before the Inquisition—this time he was found guilty of heresy. He was sentenced to life in prison—according to legend, on the day of the summer solstice of 1633.

6. It's a Day of Celebration

The solstice has been such a vastly important day throughout history that it would be impossible to list all the significant celebrations here. From Stonehenge on, the day is more-so-than-not marked by revelry—including no shortage of libations, nudity, dancing in the woods, costumes, parades, bonfires, and general merrymaking.

7. The Future of the Summer Solstice is Bright. Really, Really Bright

The gifts of the sun have been a cause for celebration for millennia—and as it turns out, based on models of stellar evolution, the sun is about 40 percent more luminous today than it was when the Earth was born some 4.5 billion years ago. And it doesn't look like it's going to slow down. Scientists estimate that in another 1 billion to 3 billion years, the sun’s looming intensity will "boil away Earth’s oceans, turning our planet into an endless desert." In which case, the winter solstice will surely become the day to frolic naked in the forest.