When Does Fall Start? The Date of the Equinox and When Meteorological Fall Begins

Introduction

As summer days draw to a close and the nights grow longer, we eagerly anticipate the arrival of fall. But when exactly does this transition occur? This article will delve into the astronomical and meteorological definitions of fall, exploring the significance of the equinox and the factors that determine the start of the autumn season.

Astronomical Fall: The Autumnal Equinox

What is the Autumnal Equinox?

The autumnal equinox marks the moment when the sun crosses the celestial equator, moving southward. This occurs around September 22 or 23 in the Northern Hemisphere and March 20 or 21 in the Southern Hemisphere.

Significance of the Equinox

During the autumnal equinox, the Earth's axis is tilted neither towards nor away from the sun, resulting in equal day and night all over the globe.

Meteorological Fall

When Does Meteorological Fall Begin?

Meteorologists define fall as the three-month period from September 1 to November 30 in the Northern Hemisphere and March 1 to May 31 in the Southern Hemisphere. This division aligns better with seasonal weather patterns and climate trends.

Factors Determining the Start of Meteorological Fall

Several factors contribute to the onset of meteorological fall, including:

• Decreasing daylight hours
• Cooler temperatures
• Increased cloud cover
• Changes in vegetation (e.g., leaves changing color)

Conclusion

The start of fall is marked by both astronomical and meteorological events. The autumnal equinox signifies the shift in the Earth's axis, while meteorological fall aligns with seasonal weather patterns. Understanding these definitions helps us appreciate the transition from summer to autumn and anticipate the beauty and changes associated with this captivating season.