Fall, autumn – whatever you call it, this season of crisp air, falling leaves, and pumpkin spice lattes is a beloved time of year for many. But exactly when does fall begin and end? The answer isn't always straightforward, and depends on which calendar you're using.
Meteorological Fall vs. Astronomical Fall: What's the Difference?
There are two main ways to define the fall season: meteorologically and astronomically. Understanding this distinction is key to answering the question of which months are in fall.
Meteorological Fall: Meteorologists, who study weather patterns, prefer a simpler, more consistent definition. They divide the year into four three-month seasons based on the annual temperature cycle. This means:
- Meteorological fall: September, October, and November.
This system is helpful for tracking weather trends and making seasonal comparisons because it uses consistent calendar months, regardless of variations in the astronomical calendar.
Astronomical Fall (Autumnal Equinox): Astronomically, fall begins with the autumnal equinox. This is the moment when the sun crosses the celestial equator, heading south, marking the start of autumn in the Northern Hemisphere. The exact date varies slightly each year, but it typically falls around September 22nd or 23rd. Astronomical fall ends with the winter solstice, around December 21st or 22nd. Therefore:
- Astronomical fall: This is a variable period lasting roughly from the autumnal equinox (around September 22nd/23rd) to the winter solstice (around December 21st/22nd).
This means the months included in astronomical fall are September, October, November, and a portion of December.
What are the Key Characteristics of Fall?
Regardless of the calendar used, fall brings some consistent characteristics:
- Falling Temperatures: A gradual decrease in average temperatures is a hallmark of fall.
- Changing Leaf Colors: The vibrant hues of red, orange, and yellow are caused by the breakdown of chlorophyll in leaves.
- Harvest Season: Fall is harvest time for many crops, including apples, pumpkins, and corn.
- Shorter Days: As the season progresses, daylight hours decrease significantly.
- Animal Migration: Many birds and animals begin their migration south for the winter.
What Months are Considered Fall in the Southern Hemisphere?
Remember that the seasons are reversed in the Southern Hemisphere. So, when it's fall in the Northern Hemisphere, it's spring in the Southern Hemisphere, and vice versa. Therefore, meteorological fall in the Southern Hemisphere is March, April, and May. Astronomical fall would then align with the vernal equinox in the Southern Hemisphere.
Frequently Asked Questions (FAQ)
Does fall always start on the same day?
No, the astronomical start of fall (the autumnal equinox) varies slightly each year, usually falling around September 22nd or 23rd in the Northern Hemisphere.
How long is fall?
Meteorological fall is precisely three months long (September, October, November). Astronomical fall is approximately three months as well, but its exact length varies slightly from year to year.
What is the difference between autumn and fall?
Autumn and fall are simply two different names for the same season. "Autumn" is more commonly used in British English, while "fall" is more prevalent in American English.
What are some typical fall activities?
Typical fall activities include apple picking, pumpkin carving, hiking in the colorful foliage, and enjoying seasonal treats like pumpkin pie and apple cider.
By understanding the nuances of both meteorological and astronomical definitions, you're better equipped to appreciate the beauty and unique characteristics of the fall season, no matter which calendar you prefer!
