立秋，是二十四节气中第13个节气，北斗星斗柄指向西南，太阳到达黄经135°，于每年公历8月7—9日交节。立秋是秋季的第一个节气，为秋季的起点。秋季从立秋起至立冬结束，其起始与结束，是天体运行的结果。进入秋季，意味着降雨、风暴、湿度等，处于一年中的转折点，趋于下降或减少；在自然界，万物开始从繁茂成长趋向萧索成熟。
立秋并不代表酷热天气就此结束，初秋期间天气仍然很热。所谓“热在三伏”，又有“秋后一伏”之说，立秋后还有至少“一伏”的酷热天气。“三伏”有初伏、中伏和末伏之分，它的日期是由节气的日期和干支纪日的日期相配合来决定的。按照“三伏”的推算方法，“立秋”这天往往还处在中伏期间，也就是说，酷暑并没有过完，真正凉爽一般要到白露节气之后。酷热与凉爽的分水岭并不是在立秋节气。Fall a leaf and know autumn
Although the autumn, but the hot weather must be after the Limit of Heat to the White Dew, will turn cool. In other words, from the Beginning of Autumn, it will be hot for a while, which is about 30 days. The folk describe a kind of climate that is very uncomfortable and even prickly as "autumn tiger". It is the weather after the Beginning of Autumn. After the Beginning of Autumn, the rain in the afternoon is gradually reduced, so it is often more sad to be exposed to the sun than in the Great heat.虽然立了秋，但炎热的天气必须过了处暑到白露时，才会转凉。换言之，从立秋开始，还会热一阵子，这段期间大约是三十天。民间形容一种热得令人十分难受，甚至有刺痛之感的气候为“秋老虎”，那正是立秋之后的天气。在立秋之后，午后的雨水逐渐减少，因此被太阳一晒，往往比大暑时觉得还要难过。According to the standard of dividing seasons according to the average temperature of climate, it is only autumn when the average temperature of five days is below 22 ℃. According to this standard, the autumn of Jianghuai area is generally in the middle and late September. After the Beginning of Autumn, although the summer heat is difficult to eliminate, although there is a residual power of "autumn tiger", the general trend is that the weather is gradually cool. The diurnal range of temperature is gradually obvious. It is often hot in the day and cool at night. In addition, the meaning of autumn also means that crops will soon mature.根据气候平均温度划分季节的标准，必须是5天的平均温度在22℃以下才算是秋天，按照这样的标准，江淮地区一般是在9月中下旬才进入秋天。立秋后虽然一时暑气难消，虽有“秋老虎”的余威，但总的趋势是天气逐渐凉爽。气温的日较差逐渐明显，往往是白天很热，而夜晚却比较凉爽。此外，秋的含义，还有庄稼快成熟的意思。
1. residual [rɪˈzɪdʒuəl] adj.剩余的;残留的 n.剩余;残渣There are still a few residual problems with the computer program.residua [rɪˈzɪdjʊə] n.(化学反应的)残基，残渣，残留物;(某种进程的)残体residuum [rɪˈzɪdʒuəm] n.(化学反应的)残基，残渣，残留物;(某种进程的)残体In these instances the food is liquid and there is little solid residuum.2. diurnal [daɪˈɜːrnl] adj.日间活动的;昼行性的;周日的Kangaroos are diurnal animals.欢迎大家留言讨论，民谚：“早立秋，凉飕飕；晚立秋，热死牛。”是什么意思？