分情況考慮 it可以指代天氣以及上文已提到過(guò)的單數(shù)可數(shù)名詞等 而that通常指代同類不同物的兩個(gè)東西
例如：
The weather here is warmer than that in Beijing
這里的that就指代北京的weather,和前一個(gè)weather是同類不同物
在肯定句中用實(shí)意動(dòng)詞,疑問(wèn)句和否定句中隨便用.例如：
You need to hand in your homework tomorrow.
Do you need to hand in your homework tomorrow?
Need you hand in your homework tomorrow?
You don't need to hand in your homework tomorrow.
You needn't hand in your homework tomorrow.
但是以物作主語(yǔ)時(shí),一般不用于情態(tài)動(dòng)詞.
如：
The flower needs watering.=The flower needs to be watered.
當(dāng)然有區(qū)別 at接小地點(diǎn) in接大地點(diǎn),當(dāng)然如果不考慮公園的大小 兩者相同
謝謝支持 望采納