Summer solstice is Friday morning

June 19th, 2013 at 4:36 pm by under Weather

Though it has felt like summer for quite some time now, our hottest season doesn’t officially begin until early Friday morning. Here is everything you ever wanted to know about the summer solstice, courtesy Deborah Byrd, and our friends at EarthSky:

Sunset at White Rock Lake, Dallas, by Lucy Bee
Sunset at White Rock Lake, Dallas, by Lucy Bee
Planning a solstice party? The 2013 June solstice takes place on Friday, June 21, at 5:04 Universal Time, or 12:04 a.m. Central Daylight Time in the U.S.

Planet Earth, as een from the sun, at the instant of the June 2013 solstice on 2013 June 21 at 5:04 Universal Time (12:04 a.m. CDT in the U.S.) Image credit: Earth and moon Viewer

It’s that beautiful time of year again in the Northern Hemisphere, when the June solstice – your signal to celebrate summer – is nearly upon us. For us in this hemisphere, this upcoming solstice, which falls on June 21 for most of us around the globe, marks the longest day of the year. Early dawns. Long days. Late sunsets. Short nights. The sun at its height each day, as it crosses the sky. Meanwhile, south of the equator, winter is about to begin.

What is a solstice?

When is the solstice where I live?

Where should I look to see signs of the solstice in nature?

Why celebrate the solstice?

How does it end up hotter later in the summer, if June has the longest day?

Waiting for dawn to arrive at Stonehenge at the summer solstice. Image from 2005 via Andrew Dunn. Wikimedia Commons.

What is a solstice? Ancient cultures knew that the sun’s path across the sky, the length of daylight, and the location of the sunrise and sunset all shifted in a regular way throughout the year.

They built monuments, such as Stonehenge, to follow the sun’s yearly progress.

Today, we know that the solstice is an astronomical event, caused by Earth’s tilt on its axis and its motion in orbit around the sun.

Because Earth doesn’t orbit upright. Instead, our world is tilted on its axis by 23-and-a-half degrees, Earth’s Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly.

At the June solstice, Earth is positioned in its orbit so that our world’s North Pole is leaning most toward the sun. As seen from Earth, the sun is directly overhead at noon 23 1/2 degrees north of the equator, at an imaginary line encircling the globe known as the Tropic of Cancer – named after the constellation Cancer the Crab. This is as far north as the sun ever gets.

All locations north of the equator have days longer than 12 hours at the June solstice. Meanwhile, all locations south of the equator have days shorter than 12 hours.

Hello summer solstice!

Hello summer solstice!

When is the solstice where I live? It comes on June 21, 2013, 5:04 UTC (12:04 a.m. CDT in the United States). That means that if you live in the western U.S., the exact time of this solstice falls late at night on June 20, for you.

See on the globe of Earth how it’s sunrise in Africa and sunset over the Pacific Ocean at the instant of this solstice? It’s high noon over eastern Asia, with the sun at zenith – or straight overhead – at the border of China and Vietnam.

The solstice happens at the same instant for all of us, everywhere on Earth. To find the time of the solstice in your location, you have to translate to your time zone.

Here’s an example of how to do that. In the central United States, for those of us using Central Daylight Time, we subtract five hours from Universal Time. That’s how we get 1:04 a.m. Central Daylight Time as the time of the 2013 June solstice (5:04 UTC minus 5 equals 12:04 a.m.).

Want to know the time in your location? Check out EarthSky’s article How do I translate Universal Time into my time? And just remember: you’re translating from 5:04 Universal Time, Friday, June 21.

June sunset from EarthSky Facebook friend Lucy Bee in Dallas. The June solstice sunset and sunrise are the northernmost of the year, as seen from around the globe.

Where should I look to see signs of the solstice in nature? Everywhere.

For all of Earth’s creatures, nothing is so fundamental as the length of the day. After all, the sun is the ultimate source of almost all light and warmth on Earth’s surface.

If you live in the Northern Hemisphere, you might notice the early dawns and late sunsets, and the high arc of the sun across the sky each day. You might see how high the sun appears in the sky at local noon. And be sure to look at your noontime shadow. Around the time of the solstice, it’s your shortest noontime shadow of the year.

If you’re a person who’s tuned in to the out-of-doors, you know the peaceful, comforting feeling that accompanies these signs and signals of the year’s longest day.

Day and night sides of Earth at instant of June 2013 solstice

Day and night sides of Earth at instant of June 2013 solstice (2013 June 21 at 5:04 Universal Time) Image credit: Earth and Moon Viewer

Why celebrate the solstice? Cultures universally have had markers, holidays, and alignments – all related to the solstice.

It has been universal among humans to treasure this time of warmth and light.

For us in the modern world, the solstice is a time to recall the reverence and understanding that early people had for the sky. Some 5,000 years ago, people placed huge stones in a circle on a broad plain in what’s now England and aligned them with the June solstice sunrise.

We may never comprehend the full significance of Stonehenge. But we do know that knowledge of this sort wasn’t isolated to just one part of the world. Around the same time Stonehenge was being constructed in England, two great pyramids and then the Sphinx were built on Egyptian sands. If you stood at the Sphinx on the summer solstice and gazed toward the two pyramids, you’d see the sun set exactly between them.

Image Credit: Flickr user Ludwig Simbajon

How does it end up hotter later in the summer, if June has the longest day? People often ask:

If the June solstice brings the longest day, why do we experience the hottest weather in late July and August?

This effect is called “the lag of the seasons.” It’s the same reason it’s hotter in mid-afternoon than at noontime. Earth just takes a while to warm up after a long winter. Even in June, ice and snow still blanket the ground in some places. The sun has to melt the ice – and warm the oceans – and then we feel the most sweltering summer heat.

Ice and snow have been melting since spring began. Meltwater and rainwater have been percolating down through snow on tops of glaciers.

But the runoff from glaciers isn’t as great now as it’ll be in another month, even though sunlight is striking the northern hemisphere most directly around now.

So wait another month for the hottest weather. It’ll come when the days are already beginning to shorten again, as Earth continues to move in orbit around the sun, bringing us closer to another winter.

And so the cycle continues.

Bottom line: The 2013 June or summer solstice takes place on Friday, June 21, 2013 at 5:04 Universal Time (12:04 a.m. CDT). This solstice – which marks the beginning of summer in the Northern Hemisphere – marks the sun’s most northerly point in Earth’s sky. It’s an event celebrated by people throughout the ages.

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