You won't lose much setting over the summer as long as the pile is not disturbed.  I've stockpiled 2 year old litter with only a little N loss and that was because I had to move the pile a few times.  As others said,  where the pile is may be more of an issue.   In MN  6 months is the max for temporary storage.   Any longer and you may get in trouble .......... depending on the county.

I've got a couple hundred tons I'd sell right now if someone really wanted it........otherwise it's sold for fall application.