Shot them in any weather, you can always pack them in ice. As for leaving them out, I only leave them out when the temp. is at least close to what my frig. is set on. Up to about 40 I would say is O.K.. If its two hot I quarter mine and bag them and let them age in a spare frig.. I age them for at least 5 days before I finish butcher them. Ill do the same if it stays below freezing all day.

Lifes a garden, dig it.