The start of later sunsets begins Thursday with the winter solstice

SEATTLE — You may have heard winter officially begins Thursday with the arrival of the winter solstice. The winter solstice will officially occur at 7:58 a.m. PST on Dec. 21, 2023, according to the National Weather Service (NWS).

But what is a solstice? And what is an equinox?

The quick answer is that after Thursday, days will start to grow longer.

RELATED | Summer solstice brings 16 hours of daylight to western Washington on longest day of year

Winter solstice

Dec. 21 annually marks the shortest day and longest night of the year in the Northern Hemisphere. This is because the Northern Hemisphere is tilted away from the sun on the winter solstice.

Thursday is the shortest day of the year, with precisely 8 hours, 25 minutes, and 25 seconds of daylight in Seattle, according to KOMO 4-Cast Meteorologist Kristin Clark.

Although daylight saving hours don't change for months, Thursday will be the turning point for short days—each day afterward will have more daylight hours.

You may notice in the winter that the sun is not as high in the sky at noontime and days feel darker.

"We all know that the Earth makes a complete revolution around the sun once every 365 days, following an orbit that is elliptical in shape," the NWS wrote on its website. "This means that the distance between the Earth and sun, which is 93 million miles on average, varies throughout the year. During the first week in January, the Earth is about 1.6 million miles closer to the sun."

"This fact may sound counter to what we know about seasons in the Northern Hemisphere, but actually the difference is not significant in terms of climate and is not the reason why we have seasons," the NWS added. "Seasons are caused by the fact that the Earth is tilted on its axis by 23.5. This can be seen graphically in the picture below."

Even though daylight slowly starts to increase after the solstice in the Northern Hemisphere, the coldest days of winter in many parts of the United States and other countries north of the equator are usually not until January, according to the National Environmental Satellite, Data, and Information Service (NESDIS). The NESDIS is part of the National Oceanic and Atmospheric Administration (NOAA).

According to NESDIS, the coldest days are after the winter solstice because the amount of solar energy arriving at the ground is less than the amount leaving the Earth for a few more weeks.

"Oceans and bodies of water, which take longer than land to heat up and cool down, keep temperatures from rising very fast," NESDIS wrote on its website. "Not until the Northern Hemisphere sees a net gain in incoming solar energy do temperatures begin their slow upward climb.

Nowhere is better to display the effects of a solstice than the most extreme examples, the poles.

In far-reaching northern areas of Earth, darkness extends for months. The North Pole does not have any sunlight or even twilight from early October until March, according to NOAA.

While the Northern Hemisphere experiences the winter solstice, the Southern Hemisphere has the opposite: the summer solstice. The hemispheres are tilted in opposite directions, and that is why a country like Australia or South Africa has a summer Christmas.

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Summer solstice

The opposite of the winter solstice is the summer solstice, occurring on the calendar on June 21 each year. The summer solstice represents the longest day and shortest night in the Northern Hemisphere.

As the year pushes on, the sun rises higher and higher.

When the sun reaches its highest point in the sky, it is called the summer solstice, according to Clark.

Much like the coldest days of the year coming after the winter solstice, the warmest days of the year are not typically on the day with the most daylight.

Because the ground, ocean, and atmosphere take time to warm, the period of maximum temperatures lags behind the period of maximum sunshine, according to Clark.

For western Washington, Clark said, late July is the typical peak of temperatures.

That's why the summer solstice may not feel like the start of summer in western Washington, but rather a typical Seattle "Juneuary".

According to NOAA, during the summer months, the North Pole sees a "midnight sun" when the sun never sets.

The sun is always above the horizon at the North Pole until the fall equinox on Sept. 21, according to NOAA.

Equinoxes

On March 21 and Sept. 21, Earth is angled approximately 90 degrees to the sun—this is when the spring and fall equinoxes occur.

During this time, both the Northern and Southern Hemispheres are exactly the same angle from the sun, according to the Smithsonian Science Education Center.

On the equinoxes, the Smithsonian said, the whole world experiences about the same amount of daylight and darkness.

At the equator, the sun is directly overhead at noon on the two equinoxes, according to the NWS.

How to enjoy the winter solstice

Many cultures view the winter solstice as a time for rebirth and celebration, according to the National Park Service (NPS).

Here are some tips from the NPS to enjoy the shortest day of the year:

• Seize the daylight and spend time outside in the sun. Take a walk and soak up the sun, if it isn't cloudy of course.
• Visit a national park and notice how the light hits the landscape. Some parks offer a winter solstice program and have day and night events.
• Enjoy the night and look up at the stars. Stars will be more plentiful with less light pollution so get out of the city if you can.
• Notice any changes of winter around you.

As days grow longer, residents of western Washington can look forward to clocks springing forward and more afternoon sun for daylight saving on March 10, 2024.