I don't think the outside temp has too much to change. However if you are sighting in your rifle and not allow enough time for the barrel to cool then you would probably have a change. My BC is dead on a cool barrel, but once it warms up it climbs about an 1 and either a 1 to the right or left. Now in all honesty your still in the kill zone but it does effect the bullet. I think as long as you sight your gun to a clean cold barrel as would your first shot be. You wont have any problems with outside temps.