Hopefully, someone else will answer. I live in Ohio so....
Here, it would be 'resting' and not growing. If this happened, I would not be too worried. I would let the roots have some exposure to air so that any damage was allowed to heal, I would water as usual (I found this bloomed better if I kept watering it--it dried quickly in my low humidity home), and keep that yellow part above the medium and dry (just the roots should be in the medium). I would keep an eye on the yellowing part but not do anything quiet yet.
Hopefully, someone who lives with your climate can advise you as orchids often grow differently in different climates.
Here is an orchid society that answers questions if you write them:
St. Augustine Orchid Society - North Florida Orchid Growing