What Seasons Are In September Verified May 2026

September is not defined by a single season but by two simultaneous, opposing transitions. For the roughly 90% of the human population living in the Northern Hemisphere, September means the cozy onset of autumn—cooler air, falling leaves, and harvest time. For the Southern Hemisphere, it means the hopeful arrival of spring—warmer breezes, flowers, and longer days. The next time someone asks, “What seasons are in September?” the most accurate answer is: It is the world’s great seasonal pivot—the first month of fall in the north and the first month of spring in the south.

Introduction

September is a unique month on the calendar, acting as a climatic bridge between the warmth of summer and the chill of winter. Unlike months such as July or January, which sit squarely within a single season, September is defined by transition. The answer to "What seasons are in September?" depends entirely on where you are standing on the globe. Due to the Earth’s axial tilt and its orbit around the sun, September marks the beginning of autumn in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere. what seasons are in september