Last winter we received around 30 inches of rain and I didn't lose a single Cattleya when the temps fell well below their suggested temperatures. All my Cattleyas are mounted without any moss. In previous years I did lose some Cattleyas from rot...but those were ones that had moss. So now I don't use any moss for any of my
CAM orchids.
Most of my Cattleyas lose their active root tips during winter...meaning they've gone dormant. But a few (Laelia crispa, Laelia purpurata) seem to have active root tips all year long.
When it comes to cold though...dormancy is a good thing. Florida has it rough because they have high temperatures one week and then freezing temperatures the next. Active growth is much more susceptible to cold damage than matured growth.
More and more I'm leaning towards orchids mounted without any moss being less susceptible to cold damage than potted orchids. Orchids mounted without any moss are going to dehydrate faster than potted orchids...which is a good thing during winter. A dehydrated orchid will have less water in its cells so in theory should take less damage when it freezes.
During summer I water at night so the lower evaporation rate provides the orchids with more time to fully hydrate.
Here's a chart comparing the average temps of Cattleya walkeriana and the avg temps of Galt, CA...