[AmericasBeekeeper]

Sure, when there is not a tornado or hurricane in the neighborhood. Seriously 55 would be better but they will survive at 50.

 

[Bens-Bees]

I shoot for 80, although it's a little more unpleasant, it gives you a lot more time to let the brood comb sit without bees on it before the brood dies.

 

[USCBeeMan]

When the nights are in the 50's and days in the 70s.

BTW, your title "When to collect a swarm". Is not accurate.

When do you collect a swarm? As soon as you get the call.

When do you collect/cutout a hive? Now that's a whole different ball game.