While many parts of the country are still experiencing hot weather, it’s comforting to know cooler temperatures could be on the way with the changing times.
Today (Tuesday, September 22, 2026) marks the Fall Equinox, or the official beginning of astronomical autumn, in the Northern Hemisphere.
This means sweaters, pumpkin-flavored snacks, and cozy fires can’t be too far away. (The opposite is true for those in the Southern Hemisphere.)
Let’s take a look at the science behind this occasion so you can wow everyone in the office with your seasonal know-how.
What are the two different ways to measure seasons?
Most modern humans measure the seasons in one of two ways.
Meteorologists have a cut-and-dried approach that focuses on annual temperatures, whole calendar months, and keeping clean records.
Winter is December, January, February, followed by spring in March, April, May. Summer begins on June 1 and lasts until August 31. Fall begins on September 1 and ends on November 30.
However, astronomers use the position of Earth in relation to the sun to determine seasons. When you measure this way, the exact dates change a bit each year.
This is because the 365-day calendar does not perfectly match up with the Earth’s orbit. There is an extra six hours every year, which is why every four years a leap day is added.
What does the fall equinox actually mean?
The Earth is tilted 23.4 degrees on its axis while it orbits the sun. This is how we get seasons.
Now imagine the equator stretching into space. At the precise moment of the fall equinox, neither hemisphere is tilted toward the sun. Additionally, that bright star crosses the celestial equator.
Gradually, the Northern Hemisphere becomes tilted away. Days become shorter and nights come quicker.
When is the official time of the Fall Equinox?
According to NASA, the exact time of the fall equinox is tonight at 8:05 p.m. ET.
Visually, there isn’t a big benefit to being outside at this moment, but maybe make a mental note to get out some extra blankets.
It may seem too soon, but like they foretold on both House of the Dragon and Game of Thrones, “winter is coming.”