I live in Central Florida near Orlando and I have a greenhouse but a majority of the local society members who don't leave their vandas outside until the temps are supposed to drop below 45F. I have three of the large Renantheras and V. Miss Joaquim, a Teres hybrid, that I have grow outside for several years and they have shown no damage with temps in the low thirties for a few hours. (Protected from frost of course)

I've been looking into this possibility for a while now and talked with many growers here in California. I've come to believe that vandas will do fine in the 40s and even 30s at night as long as airflow is restricted, they are dry and the daytime temps heat up past 65. I'm currently growing an Aerides odorata, Sedirea and Neofinetia outdoors year round. The Aerides shows the slowest growth and I'm thinking it likes to warm up a bit in the day like vandas.

As a note, min temps this past winter were 28 for an hour or so.

I'm looking to build a structure with a polycarbonate roof and 60% shadecloth on the sides to keep up RH, slow airflow and allow some heat to exist during the day time here on the Monterey Bay.

Just got two small blooming sized V. coerulea so currently trying those outdoors too.

Laelia anceps and the reed stem epidendrums have no problem with lows in the upper twenties for short periods in the event that you have an interest in them.

By the way, and ironically enough, both the Renantheras and Vanda that I spoke of are currently in bloom.

Take a look at this!
January 14 Freeze

WOW!!! I knew cymbidiums and some dendrobiums can survive frost, as mine have in the past, but not that bad. Thanks for the info.