The fall season, often called autumn, marks a distinct transition between the warmth of summer and the chill of winter. It is one of the four temperate seasons experienced outside the tropics. During this time, the environment undergoes a series of transformations, preparing for colder months.
Nature’s Colorful Display and Animal Preparations
As fall progresses, deciduous trees undergo a striking visual transformation, their leaves changing from green to vibrant hues of yellow, orange, red, and purple. This begins when trees sense shortening daylight hours and cooler temperatures. The green in leaves comes from chlorophyll, essential for photosynthesis. As fall approaches, chlorophyll production slows and existing chlorophyll breaks down, fading away.
This breakdown reveals other pigments previously masked by green. Carotenoids, responsible for yellow and orange, become visible. Additionally, some trees produce anthocyanins, creating reds and purples. Anthocyanin production is often triggered by bright light and cooler, non-freezing temperatures, especially when sugars are trapped in leaves due to reduced sap flow. Once color changes are complete, a cell layer forms at the leaf base, causing it to detach and fall.
Animals also prepare for winter. Many bird species migrate south to warmer climates where food is abundant. This instinct is often triggered by decreasing temperatures and wind patterns. Other animals, like bears, increase food intake to build fat reserves for hibernation.
Squirrels cache food during fall, burying nuts and seeds in scattered locations for winter. Their keen sense of smell helps them locate these stores later, even under snow. These preparations—migration, hibernation, or food storage—are essential survival strategies for wildlife.
Shifting Weather and Daylight Hours
Fall ushers in changes in meteorological and astronomical conditions, transitioning from summer’s warmth to winter’s cold. Temperatures gradually decrease, leading to cooler, crisper air. This drop is accompanied by a significant reduction in daylight hours and an increase in night length.
The astronomical start of fall is marked by the autumnal equinox, typically around September 22nd or 23rd in the Northern Hemisphere. On this date, the Earth’s axis is neither tilted toward nor away from the sun, resulting in nearly equal day and night across most of the globe. Following the equinox, the Northern Hemisphere continues to tilt away from the sun, causing days to shorten and nights lengthen until the winter solstice.
Fall weather patterns can become more dynamic. There is an increased chance of precipitation, often rain, as cooler air masses interact. In some regions, especially later in the season, early snowfalls can occur, signaling the transition towards winter. These atmospheric shifts influence natural phenomena and human activities.
Seasonal Traditions and Human Activities
Fall’s distinct characteristics inspire cultural traditions and human activities. Communities often celebrate the harvest season with festivals. Popular activities include visiting apple orchards for picking, exploring pumpkin patches, and navigating corn mazes. These events offer outdoor enjoyment and connection with seasonal produce.
Major holidays punctuate the fall season. Halloween, on October 31st, has roots in ancient Celtic festivals and involves trick-or-treating, costumes, and carving jack-o’-lanterns. Thanksgiving, a U.S. federal holiday, falls on the fourth Thursday of November. It is a time for gratitude, typically marked by large family meals featuring traditional foods like turkey, stuffing, and pumpkin pie.
People adapt to cooler weather by wearing warmer layers. Comforting foods and drinks, such as hot cider and hearty stews, become more prevalent. Many individuals also prepare for winter, such as readying homes.