I would love to get some input, I have two Panther Chams that I keep in screen enclosures on my patio. Since I live in South Florida this is ideal, however every now and then we get cold.
Panthers like to be warm. I would bring them in for the winter. Temps in the daytime under 80 would be too cold for them. Are you using basking and UVB lights? They would need to bask even higher than 80. Mine bask at 86 or so.
They could stay out to about 60-55*F, but that's night-time temp. You couldn't keep them outside without some heat to bask with and digest their food. I have had mine outside in the warmer months, but not at all during the few weeks of most cold, it's way too uncomfortable for them.
I'd also bring them in so they can get warm enough. We've been lucky enough that it's been a pretty warm winter so far, but when it gets cold it gets too cold for them.
We closed in our front porch for our chameleons so that we could control their humidity and temperature. The new "enclosure" also makes a great view looking out of our living room.
I have read at night down in the lower 60's. I am not sure. I keep my room at 70 at night. I have a Bearded dragon and they say 68 for him. I think a 15 degree drop from day to night is good.