Our winters are pretty similar...cold and wet. My only Cattleyas that have rotted were the ones that I mounted with some moss. But it really depends on the type of Cattleya, moss, mount and your watering schedule.
Here's one of my Cattleyas that just recently bloomed. I attached it to the tree last year...
For inspiration here are over 500 photos of
orchids growing on trees.
Just a week or so ago I submitted a proposal to attach
orchids to trees at the local botanical gardens. It has a list of orchids that several people grow outdoors year around here in Southern California.
The Santa Barbara Orchid Estate has quite a few
temperature tolerant orchids. They used to have a single page on their website that listed all their
eurythermal orchids...not sure what happened to it.
Here's a chart comparing the average temperatures of Lisbon, Portugal to Santa Barbara, USA...
38.78N | 403 ft | Lisbon, Portugal ---
34.41N | 120 ft | Santa Barbara, CA
Sources: Orchid Culture,
Weather Reports,
Temperature Charts
If you ever switch over to Flickr there's a group dedicated to
landscaping with orchids.