There are orchids that could survive even in snow. According to their response to temperature variation in the climate, orchids can be broadly classified into three categories: sensitive, intermediate and hardy.
Sensitive orchids are those which can be affected by even slight change in the different parameters, such as temperature, availability of water and sunlight, humidity etc. These orchids need extra care. When being grown outside their natural environment, it is best to grown them in controlled environments, such as inside a glasshouse. These mostly include equatorial orchids. As the equatorial region hardly sees any variation in daylight, temperature etc., therefore the orchids growing in this region are adapted to the unchanging climatic conditions. So, if your orchid comes from Amazon rainforest from countries like Brazil, Colombia, Venezuela, etc.; or from the African equatorial region which includes countries like Congo, Gabon; or from Asian equatorial regions countries like Malaysia, Indonesia; then you need to give those orchids special care.
Intermediate orchids can tolerate some degree of variations in their growing environment. These would include those orchids that are growing in the temperate regions. In these areas there is some degree of change in the climatic conditions, which are observed with the changing seasons. So, the orchids growing in this region have developed adaptations to survive slight changes in the environment.
Hardy orchids are those that grow in the tropical and mixed tropical regions. In these areas there is a wide range of variation in temperatures, day length, humidity levels etc. Consequently, the orchids growing here are adapted to survive under wide range conditions and can thus be termed as hardy.
If we take up orchids according to their habit of growing, then epiphytic orchids are adapted to survive changes in a wide range of temperature and can tolerate drought like conditions also. Most terrestrial orchids tide over unfavourable weather in form of underground parts. Still, some of the epiphytic and terrestrial are hardier than others of their type. Further, terrestrial orchids are more cold temperature tolerant than epiphytic orchids. That is why most terrestrial orchids are found in the temperate regions, while most epiphytic orchids are found in the tropics and their population dwindles with the change in the altitude.
Keeping the above information in mind, you can decide which one of your orchid can be left out in winter. It is important to note that you should know the full details of your orchid’s native habitat.