Cam break in during cold weather?

I have a very mildly built / freshened 360. (FLAT TAPPET cam + intake, 30 over pistons and a few other little things) I want to break in my motor tomorrow or Monday. The day time high is predicted to be 35* F. My friend told me that this may not be a good idea but I wanted to get more experienced peoples opinions. Is there a larger chance of failure?
Thanks
David