That's not bad at all.
(disclaimer: You should not attempt this unless you know your dragon, and what he/she prefers, and unless you know what you're actually doing and have experience...)
Iccarus was kept in the room that got the coldest in the winter, and it got to the 40's at night in there one year too. He actually got grumpy (
black bearded which is something he NEVER did, threw temper tantrums, and actually tried hissing and biting) when I moved his tank to a different room (not just the move, as he stayed like that for months after) that was warmer. When I put him back in the colder room, he turned back into his normal self. Got bright again, never hissed or bit, and quit with the tantrums. Daytime was never a problem, just nighttime temps were with him.
Again: You really have to know your dragons and what they like to be able to do certain things with them.