Old Farmer’s Almanac
The first day of winter in the Northern Hemisphere is marked by the winter solstice, which occurs 9:03 a.m. CST Sunday.
For the Northern Hemisphere, the winter solstice occurs every year between Dec. 20 through 23, most often on December 20 or 21.
The winter solstice is the day with the fewest hours of sunlight throughout the year, making it the shortest day of the year.
Thankfully, after we reach the winter solstice, the days begin to grow longer and longer again until we reach the summer solstice — the first day of summer and the longest day of the year.
Think of it this way: Although the winter solstice means the start of winter, it also means the return of more sunlight. It only gets brighter from here.
What Is the Winter Solstice
The winter solstice marks the official beginning of astronomical winter (as opposed to meteorological winter, which starts about three weeks before the solstice).
This is all thanks to Earth’s tilted axis, which means that at the solstices, half of Earth is pointed away from the Sun, and the other half is pointed towards it.
We often think of the winter solstice as an event that spans an entire calendar day, but the solstice actually lasts only a moment. Specifically, it’s the exact moment when a hemisphere is tilted as far away from the sun as possible.
What Happens on the Winter Solstice?
On the day of the winter solstice, we are tilted as far away from the sun as possible, which means that the sun’s path across the sky is as low in the sky as it can be.
Think about the daily path of the sun: It rises in the east and sets in the west, arcing across the sky overhead. During the summer, the sun arcs high in the sky, but during the winter, it arcs lower, closer to the horizon.
How can we observe the effects of solstice ourselves? On the solstice day, stand outside at noon and look at your shadow. It’s the longest shadow that you’ll cast all year. Do this again on the day of the summer solstice, and you’ll see almost no shadow.
The Sun’s Changing Path
Another way to think of this is that on the day of the solstice, the sun’s path reaches its most southerly point in the sky. For those of us in the Northern Hemisphere, this means that the sun’s path is as low in the sky as it can get — even at high noon.
The word solstice comes from the Latin sol, meaning sun, and sistere meaning to stand still. Loosely translated, solstice means “sun stands still.” Why? The sun’s path across the sky appears to freeze for a few days before and after the solstice. The change in its noontime elevation is so slight that the sun’s path seems to stay the same or stand still.
The day after the winter solstice, the sun’s path begins to advance northward again, eventually reaching its most northerly point on the day of the summer solstice.
Then, as summer advances toward winter, the points on the horizon where the Sun rises and sets advance southward each day; the high point in the Sun’s daily path across the sky, which occurs at local noon, also moves southward each day. It’s a never-ending cycle.
