"it could be rain yesterday" or "it could have been rained yesterday" Which one is correct? When we talk about a past event, actually didn't happen.
The correct way to write is
It could have rained yesterday
or
It could have been raining yesterday
It should be :
It could be raining yesterday
or
It could have been rained yesterday
Either way, the word "raining/rained" depends on your previous word. If the previous word is has/have, it needs to be a past tense of the root word which is "rained". Similarly, if the word is "be" before the action words, then you should add a "-ing" behind.
Example :
I could be sleeping.
I could have been slept.
You can refer here :
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"It could be raining yesterday" is an extremely unlikely thing to say. The only way it makes sense is as the past of "It can be raining today", which is possible, but unlikely. – Colin Fine Jul 31 '20 at 8:15
It may be learned in a proper order, like,
It could rain; It could be raining; It could have rained; and It could have been raining. It follows the order of say, It will rain; It will be raining; It will have rained; and It will have been raining; similar to future indefinite; future continuous, future perfect and future perfect continuous.
This order will help systematic study of other sentence forms. Example,
It will rain; Will it rain? Yes, it will; No, it will not (won't); Will it not (Won't it...?) When will it rain?
It will be raining; Will it be raining? Yes, it will be raining; No, it will not be raining; Will it not be (Won't it be...?); When will it be raining?
It will have rained; Will it have rained? Yes, it will have...; No it won't have...; Will it not have (Won't it have...?) When will it have rained?
I twill have been raining; Will it have been raining? Yes, it will have been raining; No it will not have been(won't have been) raining; Won't it have been raining? Why won't it have been raining?
