You may have noticed people discussing “fall” before the autumnal equinox has occurred.
That’s because astronomical and meteorological fall follow different cycles.
Meteorological Fall
Meteorological fall is a fixed period from September 1 to November 30.
Meteorologists use this system as it is simpler for record-keeping and weather analysis. With meteorological fall spanning these three months continuously, comparing trends from year to year is easier.
This structure also helps climatologists track long-term weather patterns, such as average temperatures or rainfall, because they can rely on a predictable, uniform time frame.
Astronomical Fall
Unlike meteorological fall, the Autumnal Equinox date can vary slightly each year because the Earth’s orbit isn’t perfect. While this marks a key point in Earth’s tilt, the actual weather on the ground may not match the “official” start of fall.
The Earth orbits the sun in approximately 365.25 days. That extra quarter of a day accumulates to an additional day every four years, known as a leap year. This slight shift causes the solstices and equinoxes to occur on different dates each year.
The Autumnal Equinox is considered the official start of fall in the Northern Hemisphere. It occurs at 1:19 pm on Monday, marking the same amount of sunlight and nighttime.
Why this matters
The main difference is that meteorological fall provides a consistent framework for analyzing and comparing weather patterns each year. In contrast, the autumnal equinox highlights the Earth’s movement and tilt in relation to the sun.
For meteorologists, meteorological fall is crucial when forecasting temperatures, storm trends or other long-term weather patterns. On the other hand, the autumnal equinox is a milestone for astronomers and anyone interested in the Earth’s changing relationship with the sun.
Which is more important
The autumnal equinox and meteorological fall are both important, but they highlight different aspects of the arrival of fall.
Whether you’re celebrating the seasonal milestone or analyzing weather trends, each event offers a unique perspective on the changing seasons, bringing us closer to the warmth and coziness of fall
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