If it (rain)--last night ,the ground would be wet and the te

If it (rain)__last night ,the ground would be wet and the temperature would be low today.
用词正确形式填空求解.此句有 If.would be..虚拟语气里面的 主句用would do,If从句应该用一般过去式的,表示现在事实相反.我本来用rained.但是书上答案是had rained,如果这么用后面主句应该用would have done啊.