Please do not abuse this list for your daily tinky-winky support needs!!! This list is not a replacement for using your brain. Thank you!
Google or the search engine of your choice is your friend. I used "imagemagick set tmp dir" and the very first hit seems to contain the correct answer already. That's even faster than sending a question to this list and waiting for an answer.
Thank you again for stopping to abuse this list in the future, thanks.
Kai