Mine are outdoors all the time.
Temps here never get to below maybe 2c or 3c, and that is rare.
40 f = 4.5 c and 50f = 10c.
I would have thought 50f would be more than ok.
Species Epis like Oxypetalum etc: suffer in the cold.
BTW if you grow Schlumbergeras, which I used to but don't now, if temps drop below 10c the white and light colour blooms go pink.
