Depends on how cold and (probably) how long. I have 42 eggs in the incubator right now, several of which were collected on brutally cold days and marked as "cold" because they were very chilled by the time we got to them. So far only one looks to be clear, although I have 5 that look like they started and quit by day 7. We all know not to count our chickens before they've hatched, and I think i remember reading that cold eggs have a higher likelihood of late stage embryonic death, but I'm encouraged by the development so far.