My Zygo and some dens and some Onc intergenerics tolerates the 40's as long as next day temps will rise at least 60's...at 30's and next day temps only in the low 40-50's...dicey for us here..especially if it rains..seems like similar to succulents..cold and damp bad...even if they did not get wet directly, just bad combination for orchids and succulents.
Oh just adding...my Vanda coerulea and my pleurothallids love the cold temps here. These ones, no problem.