In 2022, the autumnal equinox—also called the September equinox or fall equinox—arrives on the evening of Thursday, September 22. This date marks the start of fall in the Northern Hemisphere and spring in the Southern Hemisphere.
For those in the Northern Hemisphere, when the Sun crosses the equator going from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox. In the Southern Hemisphere, it’s the reverse. After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier. This ends with the winter solstice, after which days start to grow longer once again.
Well, about the Fall weather, let’s use two quotes to get that subtle feeling.
It is the summer’s great last heat,
It is the fall’s first chill: They meet.
–Sarah Morgan Bryan Piatt
Autumn has caught us in our summer wear.
–Philip Larkin, British poet
每年9月23日前後，是秋分，到了晝夜平分之時。詩雲：“平分秋色一輪滿，長伴雲衢千里明。”在詩人眼中，似乎是中秋滿月將秋色平分。實際上，真正平分秋色的是秋分，“晝夜均而寒暑平”。今年的秋分，北美是9月22日的傍晚。
“秋分” 的意思有二：一是太陽在這時到達黃徑180度，一天24小時晝夜均分，各12小時；二是按中國古代以立春、立夏、立秋、立冬為四季開始的季節劃分法，秋分日居秋季90天之中，平分了秋季。 秋分以後，氣溫逐漸降低，所以有“白露秋分夜，一夜冷一夜”、“一場秋雨一場寒，十場秋雨穿上棉” 和 “八月雁門開，雁兒腳下帶霜來” 的說法。
秋分也是美好宜人的時節，風和日麗，秋高氣爽，丹桂飄香。春種秋收，唐詩人李紳的《憫農》說春種一粒粟，秋收萬顆子，春天開花，秋天結果。秋分時節結果累累，螃蟹魚蝦肥美，金菊正黃。秋分也是種麥正當時，農業生產上重要的節氣。南方此時才剛變冷，則可以繼續農作，延續到秋天結束霜降為止。