Can I still use butter that's been left out for 2 days? I bought butter in 1/4 sticks (one pound box) and left it in my trunk by accident.  It's been very cold 35-50° F (2-10° C) at night/day. It's been 48 hours.

Can I still use it? It's still in it's original container/box.
Yes, that should be fine. Plenty of people keep butter on the counter, so a couple days at below 50 is no big deal.