The term Three Furnaces refers to the especially hot and oppressively humid summer weather in several major cities in the Yangtze River Valley

Yangtze River

The Yangtze, Yangzi or Cháng Jiāng is the longest river in Asia, and the third-longest in the world. It flows for from the glaciers on the Tibetan Plateau in Qinghai eastward across southwest, central and eastern China before emptying into the East China Sea at Shanghai. It is also one of the...

, within China. It was coined during the Republican period of China, and refers to the following cities:

• Chongqing
  Chongqing
  Chongqing is a major city in Southwest China and one of the five national central cities of China. Administratively, it is one of the PRC's four direct-controlled municipalities , and the only such municipality in inland China.The municipality was created on 14 March 1997, succeeding the...
  
  
• Wuhan
  Wuhan
  Wuhan is the capital of Hubei province, People's Republic of China, and is the most populous city in Central China. It lies at the east of the Jianghan Plain, and the intersection of the middle reaches of the Yangtze and Han rivers...
  
  
• Nanjing
  Nanjing
  ' is the capital of Jiangsu province in China and has a prominent place in Chinese history and culture, having been the capital of China on several occasions...
  
  

Sometimes, Changsha or Nanchang

Nanchang

Nanchang is the capital of Jiangxi Province in southeastern China. It is located in the north-central portion of the province. As it is bounded on the west by the Jiuling Mountains, and on the east by Poyang Lake, it is famous for its scenery, rich history and cultural sites...

 are added, making the Four Furnaces . In addition to the above 5 cities, Hangzhou

Hangzhou

Hangzhou , formerly transliterated as Hangchow, is the capital and largest city of Zhejiang Province in Eastern China. Governed as a sub-provincial city, and as of 2010, its entire administrative division or prefecture had a registered population of 8.7 million people...

 and Shanghai

Shanghai

Shanghai is the largest city by population in China and the largest city proper in the world. It is one of the four province-level municipalities in the People's Republic of China, with a total population of over 23 million as of 2010...

 are added to form the Seven Furnaces (七大火炉).

Yet the above names originate mainly from popular opinion, not necessarily on the basis of data. Meteorologists only give the title "Three Furnaces" to Fuzhou

Fuzhou

Fuzhou is the capital and one of the largest cities in Fujian Province, People's Republic of China. Along with the many counties of Ningde, those of Fuzhou are considered to constitute the Mindong linguistic and cultural area....

, Hangzhou, and Chongqing. The next seven hottest cities (2000—2009), are Changsha, Wuhan, Haikou

Haikou

Hǎikǒu , is the capital and most populous city of Hainan Province, in the People's Republic of China. It is situated on the northern coast of Hainan, by the mouth of the Nandu River...

, Nanchang, Guangzhou

Guangzhou

Guangzhou , known historically as Canton or Kwangchow, is the capital and largest city of the Guangdong province in the People's Republic of China. Located in southern China on the Pearl River, about north-northwest of Hong Kong, Guangzhou is a key national transportation hub and trading port...

, Xi'an

Xi'an

Xi'an is the capital of the Shaanxi province, and a sub-provincial city in the People's Republic of China. One of the oldest cities in China, with more than 3,100 years of history, the city was known as Chang'an before the Ming Dynasty...

, and Nanning

Nanning

Nanning is the capital of the Guangxi Zhuang Autonomous Region in southern China. It is known as the "Green City" because of its abundance of lush tropical foliage.-History:...

. Unlike the other cities, Xi'an, the capital of Shaanxi

Shaanxi

' is a province in the central part of Mainland China, and it includes portions of the Loess Plateau on the middle reaches of the Yellow River in addition to the Qinling Mountains across the southern part of this province...

province, lies within the northwest.