(North America, Europe, most of Asia): Fall runs from the September equinox to the December solstice .

The iconic "changing of the leaves" is actually a process of unmasking. As days shorten and sunlight becomes less intense, deciduous trees stop producing chlorophyll—the pigment that keeps leaves green. This allows other pigments, like (yellows and oranges) and anthocyanins (reds and purples), to finally take center stage before the leaves eventually drop. The "Cozy" Aesthetic: A Cultural Phenomenon

Determining when fall "officially" starts depends on whether you follow the stars or the thermometer.

This is the traditional, calendar-based definition most people learn in school. It is tied to the Earth’s 23.5-degree tilt and its orbit around the sun. Fall begins with the —the precise moment when the sun crosses the celestial equator, heading south. On this day, day and night are nearly equal in length (approximately 12 hours each).

Visiting pumpkin patches, navigating corn mazes, and the "Back to School" rush that signifies a return to routine. The Best Fall Blog Post Ideas for Beginner Bloggers

For the most accurate "lived experience" in the Northern Hemisphere, view fall as a gradient that begins September 1st (meteorological) but hits its peak vibrancy roughly mid-September through late October.