Question

but it rained all day

If the weather had been better ,we could have had a picnic.But it(rained) all day 为什么用过去时态
If the weather had been better ,we could have had a picnic.But it(rained) all day 为什么用过去时态

Answer 1

If the weather had been better ,we could have had a picnic.
这是个表示与过去事实相反的虚拟语气的句子,意思和含义是：如果天气好些的话,我们就可以去野餐了（实际是,过去的时候天一直不好,所以我们野餐没有去成）
因此后面it rained all day,表示实际上过去一整天下雨.
或者用过去进行时也可以,it was raining all day.整天都“在”下雨（强调在下雨）