the weather is cooler in Qingdao than

问题补充：

the weather is cooler in Qingdao than

答案：

因为外国人讲话也是不忌讳重复,原句应该是

the weather is cooler in Qingdao than the weather in Wuhan

但是这样很累赘,所以用that代替了the weather

这种用法在含有 than 的表示比较的句子中很常用的

======以下答案可供参考======

供参考答案1:

that,此处 = the weather

供参考答案2:

that 代表前句当中的 weather,也就是青岛当地的天气。