vårat is a colloquial form of vårt. I recommend never using it in writing, it looks very informal.
våras is not a form of the word vår as in 'our', though there is a verb våras which is related to the word vår 'spring'. It is used like this: Det våras meaning 'it is becoming spring' or 'spring is coming', also in an abstract sense to mean 'things are looking up'. Most notably this verb was used to translate the titles of Mel Brooks films starting with 'Young Frankenstein' = Det våras för Frankenstein. It's a pretty rare verb otherwise :)