What's the weather like in Changsha, Hunan?

How come it's really hot in summer in Changsha, but it's not as hot as the three traditional stoves of Chongqing, Nanjing and Wuhan, and Changsha is the fourth at best.

In winter, Changsha can't compare with the north. The north cannot move below zero. The reason why Changsha is cold is because there is heating in the north ~

If the air quality in cities is poor, the countryside is ok, and that's (usually) it.