When Does Fall Begin? The Autumn Equinox Explained

Is today the first day of fall? For many, the arrival of fall signals cozy sweaters, pumpkin spice lattes, and vibrant foliage. But pinpointing the exact start date of this beloved season can be a bit confusing. Let's dive into when fall officially begins and what marks its arrival.

Defining the First Day of Fall

The first day of fall, also known as the autumnal equinox, isn't a fixed date. It varies slightly each year but generally falls on September 22nd or 23rd in the Northern Hemisphere. In 2024, the autumnal equinox will occur on September 22nd. This date marks the moment when the sun crosses the celestial equator, transitioning from the Northern Hemisphere to the Southern Hemisphere.

What is the Autumnal Equinox?

The term "equinox" comes from the Latin words "aequi" (equal) and "nox" (night). During the equinox, day and night are approximately equal in length. After the autumnal equinox, the days become shorter than the nights as we head towards winter. This transition is a key indicator of the change in seasons.

Meteorological vs. Astronomical Fall

It's worth noting that there are two ways to define the start of fall: meteorological and astronomical.

• Meteorological Fall: Defined by meteorologists, this season begins on September 1st and ends on November 30th. This fixed date helps in tracking and comparing seasonal weather patterns.
• Astronomical Fall: This is based on the Earth's position in relation to the sun and is marked by the autumnal equinox.

Signs of Fall

Besides the calendar, several signs indicate that fall has arrived:

• Changing Leaves: As temperatures drop, the chlorophyll in leaves breaks down, revealing vibrant yellows, oranges, and reds.
• Cooler Temperatures: The crisp air and cooler temperatures are a welcome change after the heat of summer.
• Harvest Season: Many fruits and vegetables ripen in the fall, making it a prime time for harvesting.
• Wildlife Preparations: Animals begin to prepare for winter, storing food and seeking shelter.

Why Does the Date Vary?

The autumnal equinox doesn't fall on the same date every year due to the Earth's elliptical orbit around the sun and the tilt of its axis. These factors cause slight variations in the timing of the equinox.

Celebrating the Season

Whether you follow the meteorological or astronomical definition, fall is a time to celebrate. Enjoy the changing colors, cozy up with a warm drink, and embrace the beauty of the season.

So, is today the first day of fall? Check your calendar! Whether it's September 1st or the date of the autumnal equinox, get ready to enjoy all that fall has to offer.