Autumn Equinox Signals Change: What to Expect This Season

The arrival of fall is marked by the autumnal equinox on September 23, 2023, at 2:19 p.m. Eastern Time. This moment signifies a shift in seasons, with shorter days and cooler temperatures dominating the Northern Hemisphere. The sun will rise due east and set due west, creating nearly equal daylight and darkness across the globe. As the sun’s direct rays move southward, countries in the Southern Hemisphere, such as South America, parts of Africa, and Australia, will begin to experience warmer days.

With the onset of autumn, the Northern Hemisphere is poised for a period of atmospheric transition. The polar vortex will start to expand, and the jet stream will shift southward over the contiguous United States. This change is expected to bring increasingly turbulent weather patterns, including significant storm systems that could lead to strong winds, severe weather, and, eventually, winter storms and blizzards.

As daylight diminishes, regions will experience a notable reduction in the amount of sunlight. For instance, Washington, D.C., will lose approximately 2 minutes 30 seconds of daylight each day, while Boston will see a daily decrease of 2 minutes 49 seconds. In contrast, Miami will lose just under a minute and a half of daylight on average each day. The variance in daylight loss is more pronounced in the northern parts of the U.S., which see a greater decline in day length compared to southern states. By the end of October, areas like South Florida and the Texas-Mexico border will have lost around 40 minutes of daylight, while northern New England and the Pacific Northwest could lose close to 90 minutes.

This phenomenon is a result of the Earth’s axial tilt of approximately 23.5 degrees. During the summer months, the Northern Hemisphere tilts toward the sun, resulting in longer days and warmer temperatures. Conversely, winter sees the hemisphere leaning away from the sun, leading to shorter days and colder weather. The equinox represents a unique moment when both hemispheres receive equal sunlight, a concept reflected in the term “equinox,” which translates to “equal night” in Latin.

As fall progresses, many will also notice the striking transformation of foliage. The reduction in sunlight limits the leaves’ ability to produce food, leading to a change in their color. Leaves primarily rely on chlorophyll, which gives them their green hue and plays a crucial role in photosynthesis. As chlorophyll diminishes, other pigments such as carotenoids and anthocyanins become more visible, revealing vibrant shades of yellow, orange, and red. While temperature fluctuations can influence leaf color, the primary factor is the availability of sunlight, which decreases significantly as autumn progresses.

Additionally, the scent that often accompanies autumn is multifaceted. As leaves fall, they release various gases through tiny pores known as stomata. These gases, including terpenes and isoprenoids, contribute to the characteristic aroma of the season. Terpenes, a class of hydrocarbons, are responsible for many plant scents, such as the smell of pine from conifer trees. The decomposition of plant matter also plays a role in the seasonal scent, as organisms like Geotrichum candidum contribute to the natural odors associated with autumn.

As people prepare for the changes that autumn brings, from cooler weather to vibrant landscapes, the transition serves as a reminder of nature’s cyclical patterns. The coming months will not only see a shift in the environment but also in the activities and traditions that define this time of year. Whether it is enjoying the colorful foliage or preparing for the winter ahead, the autumn equinox marks the beginning of a season rich with change and beauty.