How Many Days Until Autumn?

The September equinox happens when the Sun crosses the celestial equator, moving from the northern to the southern sky. On this day, sunlight is spread almost evenly across the planet.

Because of this, day and night are nearly equal in length all over the world. The word equinox itself comes from Latin, meaning "equal night," which sums up exactly what makes the day special.

Autumn usually begins around September 22 or 23 each year in the Northern Hemisphere. The date is not fixed because the Earth takes roughly 365.24 days to circle the Sun.

That extra quarter of a day slowly adds up and is corrected by leap years, which is why the exact start can shift by a day from one year to the next. In rare cases it can even fall on September 21 or 24, though this is unusual.

Autumn weather is defined by a steady drop in temperature as the warmth of summer fades. Mornings turn cool and crisp, and the air often feels fresh and dry, though conditions vary widely from one region to another.

Daylight also shrinks noticeably through the season. After the equinox, the nights grow longer than the days, and by late autumn many places see the sun set in the late afternoon. This shift in light is one of the clearest signs that winter is on its way.

One of autumn's most famous features is the changing color of the leaves. As days shorten and temperatures fall, trees stop making chlorophyll, the green pigment that powers their leaves through spring and summer.

Once the green fades, the yellows, oranges, and reds that were hidden underneath finally show through. Eventually the leaves fall away completely, leaving trees bare for the winter. This yearly display draws visitors to forests and parks around the world, a tradition often called leaf peeping.