Which one would be correct?
- I wish it weren't raining today.
- I wish it wasn't raining today.
- I wish it were raining today.
- I wish it was raining today.
Which one would be correct?
The fact that you wish something was or wasn't true means you should use the indicative. You are stating that something is factually one way or another, and wishing for the situation to be reversed. So "I wish it wasn't raining today" and "I wish it was raining today" are how to express those concepts.
If you were trying to imply something contrary to fact, then were would be the way to go.
If I were you, I wouldn't be wishing it wasn't raining: rain is good for your garden.
Edit: Because Stan Rogers, whose opinion I respect, has weighed in with the polar opposite viewpoint from mine, I feel obliged to elaborate.
Morton S. Freeman, writing in A Treasury for Word Lovers, elaborates on a parallel idea using if clauses:
Some people have a mistaken belief that a clause beginning with if must always be in the subjunctive mood, reflecting doubtful fulfillment of the condition or a condition contrary to fact. This is not so. A clause introduced by if may express a simple condition relating to the past and take the indicative form of the verb. For example, in "If Allan was there, he was drunk," the if clause introduces a supposition, hence a verb in the indicative mood. And so with the sentences "If Curran was absent, he was probably out of town" and "If I was long-winded, I'm sorry." None of the examples imply doubt or suggest circumstance contrary to fact, as in "If I were President, I wouldn't pardon him." [Emphasis added.]
I think you can see the parallel here. Far from indicating a circumstance contrary to fact, the "I wish" construction is lamenting an actual fact. So subjunctive mood is not called for.
Were and weren't are correct (and the subjunctive mood is weird). When you express a wish, the past subjunctive is the correct tense and mood. [Link added -- I did say the subjunctive is weird.]
Both forms are fine.
I wish it was…
I wish it were…
The traditional formal line on this is unclear. I’d always understood that the subjunctive, were, is the correct mood to use with wish; and Wikipedia, various other online sources, and Stan Rogers agree. However, Robusto disagrees articulately… so until someone finds what a serious authoritative modern grammar says on this, it seems open.
However, either form is undoubtedly acceptable — and indeed, this has been the case for at least two centuries. Comparing
I wish I was and
I wish I were in COHA shows that their relative popularities have fluctuated —
was was the commoner through the 19th century and is again in recent decades, while
were predominated in the early/mid 20th century — but that the difference between the two has never been overwhelming either way. For the 2000’s, COHA shows
I wish I was to be roughly twice as frequent as
I wish I were. (Comparing
I wish it was and
I wish it were shows similar fluctuations, but with a rather smaller sample size, so the trends are less clear.)