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December 21

Winter solstice lesson: why December 21 is the shortest day in the north and the longest in the south

A free, no prep winter solstice lesson for grades 3 to 8: Earth's tilt, real daylight data for four cities, and verified solstice times for 2026 to 2030.

Grades
3 to 8, with changes for younger and older
Time
25 minutes
Prep
None. Project this page or read from it.
You need
Paper and pencil for each student, Optional: a ball and a lamp or flashlight, if the room has them. The lesson works without them.

What it is

The December solstice happens when Earth's tilt away from the Sun is at its maximum for the Northern Hemisphere. At that moment the Sun is directly over the Tropic of Capricorn, 23.5 degrees south of the equator. In the Northern Hemisphere it is the shortest day of the year, and after it the days begin to lengthen.

In the Southern Hemisphere the same date brings the longest day of the year. Earth's tilted axis causes the seasons, not its distance from the Sun, so the two hemispheres have opposite seasons at the same time. At the South Pole the Sun does not set for 24 hours.

The solstice is a moment, not a whole day. NASA says it falls on December 21 or 22. The U.S. Naval Observatory lists the December solstice in Eastern Standard Time as Monday, December 21, 2026 at 3:50 p.m.; December 21, 2027 at 9:42 p.m.; December 21, 2028 at 3:19 a.m.; December 21, 2029 at 9:14 a.m.; and December 21, 2030 at 3:09 p.m.

A surprise for students: the solstice is the shortest day, but it does not bring the earliest sunset or the latest sunrise. NOAA says those come a couple of weeks before and after the solstice.

How to run it

25 minutes, 5 steps. The time on the left is when each step starts.

  1. 0:00

    Warm-up

    4 min
    On the board

    December 21, 2026. New York: sunrise 7:17 a.m., sunset 4:32 p.m. Buenos Aires, Argentina: sunrise 5:37 a.m., sunset 8:06 p.m. Which city gets more daylight? About how much more?

    You do
    • Show both cities. Students work out the hours of daylight alone for two minutes.
    • Take answers. New York has about 9 hours 15 minutes of daylight. Buenos Aires has about 14 hours 29 minutes. The difference is about 5 hours 14 minutes.
    • Do not explain why yet. Ask for guesses and write them on the board.

    Say: Same date, same planet, very different day. Hold on to your guess.

  2. 4:00

    The solstice in five facts

    5 min
    On the board
    • The December solstice happens when Earth's tilt away from the Sun is at a maximum for the Northern Hemisphere.
    • In the Northern Hemisphere it is the shortest day of the year. After it, the days begin to lengthen.
    • At the December solstice the Sun is directly over the Tropic of Capricorn, 23.5 degrees south of the equator.
    • Earth's tilted axis causes the seasons, not its distance from the Sun. The two hemispheres have opposite seasons.
    • In 2026 the December solstice is Monday, December 21 at 3:50 p.m. Eastern Standard Time.
    You do
    • Read the five facts aloud, one at a time.
    • After fact 4, go back to the guesses on the board. Cross out any guess that says Earth is closer to the Sun in summer, and ask why the opposite seasons in the two hemispheres rule it out.
    • After fact 5, tell students the time is a moment, not a whole day.

    Say: Winter is not about distance. It is about tilt.

  3. 9:00

    Draw the tilt

    8 min
    On the board

    Draw the Sun on the left of your page. Draw Earth on the right as a circle with a tilted axis. The North Pole leans away from the Sun. Draw the equator and the Tropic of Capricorn (23.5 degrees south). Draw a dot for New York in the north and a dot for Buenos Aires in the south. Shade the side of Earth that faces away from the Sun.

    You do
    • Draw the diagram on the board as students draw it on paper: Sun on the left, Earth on the right, axis tilted so that the top leans away from the Sun.
    • Point out that the tilt of Earth's axis is 23.5 degrees.
    • Ask: as Earth spins, does the New York dot spend more time in the lit half or the shaded half? What about the Buenos Aires dot? Answers: New York spends more than half of each spin in the shade, so its day is short. Buenos Aires spends more than half in the light, so its day is long.
    • Optional: if the room has a ball and a lamp or flashlight, show the same thing by tilting the ball away from the light and turning it. The lesson works without them.

    Say: The tilt changes how long the day lasts and how directly the sunlight arrives.

  4. 17:00

    Real daylight data

    5 min
    On the board

    Daylight on December 21, 2026: Anchorage, Alaska (61 degrees north) 5 hours 27 minutes. New York (41 degrees north) 9 hours 15 minutes. Miami (26 degrees north) 10 hours 32 minutes. Buenos Aires (35 degrees south) 14 hours 29 minutes. Daylight on June 21, 2026: New York 15 hours 6 minutes. Buenos Aires 9 hours 50 minutes. What pattern do you see?

    You do
    • Students rank the four cities from least to most daylight and write the pattern in one sentence.
    • Draw out two patterns. In the Northern Hemisphere, the farther north the city, the shorter the December day. And the two hemispheres flip between December and June.
    • Ask which city is in the Southern Hemisphere and what its numbers say.
  5. 22:00

    Exit ticket

    3 min
    On the board

    Finish the sentence: On the December solstice the Northern Hemisphere has its shortest day because ...

    You do
    • Students answer on a scrap of paper and hand it to you at the door.

Discussion questions

Open an answer when you want it.

Why does the Southern Hemisphere have its longest day at the same time the Northern Hemisphere has its shortest?

Earth's axis is tilted, so in December the Northern Hemisphere leans away from the Sun while the Southern Hemisphere leans toward it. NASA says the two hemispheres have opposite seasons.

If Earth were closer to the Sun in summer, would that explain the seasons? What evidence says no?

No. NASA says Earth's distance from the Sun is not the cause of the seasons. Evidence: when it is winter in the north it is summer in the south, but the whole planet is at one distance from the Sun.

Is the winter solstice the day with the earliest sunset?

No. NOAA says the solstice does not bring the earliest sunset or the latest sunrise. Those come a couple of weeks before and after the solstice. The solstice is the day with the least daylight in the north.

Exit ticket

Finish the sentence: On the December solstice the Northern Hemisphere has its shortest day because ...

Earth's axis is tilted, and in December the Northern Hemisphere is tilted farthest away from the Sun.

Make it fit your class

Younger students

For kindergarten to grade 2, skip the data and the diagram. Say that the days are shortest now and will slowly get longer. Students draw a short-day sun path and a long-day sun path across the sky and tell you which one is the winter day.

Older students

For grades 9 to 12, have students graph the December daylight against latitude for the four cities and describe the pattern. Then ask why Anchorage has about 19 hours 23 minutes of daylight on June 21, 2026 while Miami has about 13 hours 45 minutes, and what that says about how latitude and tilt work together.

Where the facts come from

Image credits

  • A Low Angle Shot of a Leafless Trees on a Snow Covered Ground by mali maeder, Pexels License. Source.

Updated October 31, 2026