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The winter solstice happens on Monday, December 21, 2020. This is the astronomical first day of winter in the Northern Hemisphere and the shortest day of the year. What happens at the winter solstice? Why is the solstice important? Enjoy solstice facts and folklore from The Old Farmer’s Almanac.
WHEN IS THE FIRST DAY OF WINTER?
The first day of winter in the Northern Hemisphere is marked by the winter solstice, which occurs on Monday, December 21, 2020, at 5:02 A.M. EST.
For the northern half of Earth (the Northern Hemisphere), the winter solstice occurs annually on December 21 or 22. (For the Southern Hemisphere, the winter solstice occurs on June 20 or 21.) The winter solstice is the day with the fewest hours of sunlight in the whole year, making it the “shortest day” of the year. Thankfully, after we reach the winter solstice, the days begin to once again grow longer and longer 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!
The winter solstice marks the official beginning of astronomical winter (as opposed to meteorological winter, which starts about three weeks prior to the solstice). The winter solstice occurs once a year in each hemisphere: once in the Northern Hemisphere (in December) and once in the Southern Hemisphere (in June). It marks the start of each hemisphere’s winter season. When one hemisphere is experiencing their winter solstice, the other is simultaneously experiencing their summer solstice!
This is all thanks to Earth’s tilted axis, which makes it so that one half of Earth is pointed away from the Sun and the other half is pointed towards it at the time of the solstice.
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 it can be. This is shown in the diagram below.
The winter solstice holds significance across a variety of cultures, as it signals the changing of the seasons. Some ancient peoples even marked the solstice using huge stone structures, like Newgrange in Ireland. In some cultures, the solstice traditionally marked the midway point of the season rather than the start of it, which explains why holidays such as Midsummer Day are celebrated around the first day of summer.
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 day of the solstice, 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.” In the Southern Hemisphere, it’s the opposite: The Sun’s path will be high in the sky on the winter solstice—directly overhead at noon at the latitude called the Tropic of Capricorn, which is an imaginary line that circles the Earth, running through parts of South America, southern Africa, and Australia.
The word solstice comes from Latin sol “sun” and sistere “to stand still.” So, loosely translated, it means “sun stand still.” Why? For a few days before and after the solstice, the Sun’s path across the sky appears to freeze. 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!
→ Observe the changing day length in your area with our Sunrise and Sunset Times Calculator.
Summer Solstice
When we reach the summer solstice on June 20, 21, or 22, the Sun will reach its most northerly spot, directly overhead at the Tropic of Cancer (which runs through Mexico, northern Africa, and southern Asia). The summer solstice is the longest day of the year (the day with the most daylight hours) and marks the beginning of summer. Learn more about the summer solstice!
Equinoxes
You may also be familiar with the term “equinox.” In the spring (March) and the fall (September), the Sun’s path bring it directly above Earth’s equator. Equinox means “equal,” as day and night on the equinoxes are of roughly equal length.
See our SEASONS page for a diagram and dates of all seasons.
The day of the winter solstice is the shortest day of the year, which means that it’s the day in which we experience the least amount of daylight. Logically, it would make sense to assume that this is also the coldest day of the year, since we are exposed to less warmth-giving sunlight on this day than at any other time. But this is not true.
There are a lot of factors that affect the temperature of a location on any given day, including altitude, snow cover, and large-scale weather patterns. Snow cover, for example, partially blocks solar radiation from being absorbed by the Earth, which results in less heat being released and an overall drop in temperature. Because of these factors, it’s not possible to point to the same date year after year and call it the coldest day.
In the United States, the coldest days of the year tend to occur between mid-December and late January, so while it’s certainly possible that the coldest day of the year could also be the day of the winter solstice, that’s not usually the case!
There is not a black-and-white answer to this question—it depends on which definition of “winter” you follow:
Because an almanac is traditionally defined as a “calendar of the heavens,” we at The Old Farmer’s Almanac follow the astronomical definition of the seasons, which states that each of the four seasons starts on a solstice or equinox.
Learn more about the Reasons for the Seasons.
However, that doesn’t mean that the meteorological definition is incorrect. It is important for meteorologists to be able to compare climatological statistics for a particular season from one year to the next—for agriculture, commerce, and a variety of other purposes. Thus, meteorologists break the seasons down into groupings of three months. Meteorological winter starts on December 1 and includes December, January, and February.
Did you know? For the ancient Celts, the calendar was based around the solstices and equinoxes, marking the Quarter Days, with the mid-points called Cross-Quarter Days.
Learn more about the Celtic calendar.
The solstice has been celebrated since ancient times by cultures around our planet.
Thousands of people celebrate the solstices at Stonehenge in England. Due to the alignment of the stones, experts acknowledge that the design appears to correspond with the use of the solstices and possibly other solar and lunar astronomical events in some fashion.
At sunrise at Stonehenge on the summer solstice (longest day of the year), the Sun appears to balance perfectly on one of the stones.
There are several theories as to why the structure was built, including that the area was used as a temple to worship the Sun; as a royal burial ground; and/or as a type of astronomical observatory. However, because none of these theories has been proven correct as yet, the true reason (or reasons) for Stonehenge’s existence remains a mystery.
Read more about Ancient Sites Aligned with the Solstice and Equinox.
Here at the Almanac, we love our weather folklore. Here are just a few (of the many) proverbs that we have collected in our archives:
Read more winter weather folklore.
