I don't know what the lowest temp they can handle would be, but mine have been outside in the tractor since they were 3 weeks old, and we've gotten into the high 40's low 50's at night time, they've seemed to handle it well.
I plan on processing at 8-9 ish weeks, I'll go be weight, aiming for 8-10lbs live weight. I think the big variable in processing time lies in the feeding regiment you follow, I feed by weight twice a day, so my birds will take a little longer than someone that feeds free choice.
Thanks
