I don't know much about orchids, but I do know that the coldest place in the house at night, in Canada, is near the windows. It would probably be Ok in the day if you moved them at night.

Your best bet to know for sure is to ask at the Orchid forum.

Cattleyas need as much sun as possible. I think the southern window would be OK, but if they have not had direct sun befoe, move them there over seveal days - a couple of hours each day, until they get used to the light.

If Cattleyas get too much sun the leaves will get very light green - they almost look sick, but then they flower well.

They will not like the cold so keep them back a few inches from the window.

Yes and also because of our dry winters, take a tray and fill it up with small pebbles and water. then take your orchids and let them stand on the pebbles without touching the water. As the water evaporates, it creates a nice humid environment for the orchids.

A southern exposure is fine for cattleyas and their intergeneric hybrids, but, with shortened daylight hours make sure not to feed them until new growth has begun. All my orchids (in the house and greenhouse)commence their feedings around the middle of may until october. The suggestions that the other posters have submitted will indeed produce healthier plants. Healthier plants = more profuse blooming