立秋是二十四节气的第十三个节气，更是秋天的第一个节气，标志着孟秋时节的正式开始。立秋过后，梧桐树开始落叶，因此有“落叶知秋”的成语。今年的立秋始于8月7日。
立秋后，往往有数天炎暑逼人，无异于盛夏，俗称“秋老虎”，比喻其凶猛可怕，犹如老虎。秋老虎从气象学的角度来说是指三伏出伏后短期回热的天气，一般发生在8月至9月之间，天气特征是早晚清凉、午后高温暴晒。
在清朝，民间流行在立秋这天以悬秤称人，将体重与立夏所称的体重对比来检验当年夏季的健康状况。如果瘦了就要在立秋后“贴秋膘”，通过食补来增肥。一般首推食用肉类，“以肉贴膘”。
《立秋》
一叶梧桐一报秋，稻花田里话丰收。
虽非盛夏还伏虎，更有寒蝉唱不休。
 
立秋的气候是由热转凉的交接节气，
也是阳气渐收，阴气渐长，由阳盛
逐渐转变为阴盛的时期，是万物成
熟收获的季节。
“啃秋”，寓意炎炎夏日酷热难熬，忽逢立秋，将其咬住，与“咬春”相似，人们认为立秋之时吃一些东西能预防疾病。大部分地区会在立秋当日吃西瓜，也有吃甜瓜、饺子和玉米的省份。啃秋抒发的，实际上是一种丰收的喜悦。
古人常在立秋时节举办举重比赛，则借举重的器物，以比试体力的大小。拉弓比赛也非常流行，以拉弓弦到圆满为标准，其重量以石来计算。民间则通常用石锁、石担来比，力气大的，不但能只手高举，而且可以上下盘旋挥舞，随意做出各种动作。
在浙江杭州一带有立秋日食秋桃的习俗。每到立秋日，人人都要吃秋桃，每人一个，桃子吃完要把桃核留藏起来。等到除夕，不为人知地把桃核丢进火炉中烧成灰烬，人们认为这样就可以免除一年的瘟疫。
“摸秋”的风俗流行于江苏盐城北部地区。立秋日晚上，人们可以在别人家的瓜园中摸回各种瓜果，俗称摸秋。丢了瓜果的人家（也称丢了“秋”的人家），无论丢多少，也不追究。如果摸到瓜果，父母就认为孩子将来不愁吃喝，事事顺利。人们将摸秋视为游戏，算不上小偷小摸之劣行。但是，过了立秋时节，父母就要严格教育孩子，不可以再去偷拿他人的一针一线。
The traditional Chinese lunar calendar divides the year into 24 solar terms. Start of autumn, the 13th solar term of the year, begins on Aug 7 this year and ends on Aug 22.
Although start of autumn signals beginning of fall, hot weather still lingers. "Autumn tiger" or "Indian summer", refers to a month-long period of hot weather after the start
of autumn.  Because of decreasing precipitation, it is even more sweltering during this period than during major heat (July 23-August 7).

People often weigh themselves on the first day of start of autumn and compare their weight to what it was at the start of summer. If one has lost weight during the summer, according to Chinese customs, he or she needs to flesh out at the beginning of autumn by eating more, especially meat.

Start of autumn is a big solar term for farmers as it is a time for harvest. 
As a popular saying goes in Chinese: "If it rains on the day of the start of autumn, a good harvest is expected."
"Biting autumn" is a folk custom that signifies biting onto autumn and not letting it go. Many believe that eating a particular kinds of food on start of autumn, in most cases watermelon, can bring along a healthy year. "Biting autumn" can be taken as a sentimental gesture that celebrates good harvest. 
In ancient China, weight lifting contests were often held during start of autumn. People lifted rocks, pulled arches with weights and tossed locks made of rocks in order to demonstarte their strength.
In Hangzhou, Zhejiang province, people eat peaches on the start of autumn. The peach pits are kept until New Year's Eve and thrown into the stove then burned into ash, so as to "burn" out any possible illnesses that may harm one's health.
There is the custom of "Touching autumn" in the northern part of Yancheng, Jiangsu province. On the eve of start of autumn, people can take fruits and vegetables as they like from private or public gardens for good luck. Owners will not be angry, no matter how much they lose. Many gardeners even leave some mellow fruits in the field on purpose for the guests during the night.

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